GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Korean Gate => Topic started by: Hobbyman2007 on August 15, 2018, 10:52:08 PM
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My new Winchester / Blizzard .357 just arrived but unfortunately I’m away on business for the next ten days . I’ll be documenting the conversion process to .257 cal as I go . I don’t believe this has been done before and I’m sure I’ll be looking for some guidance along the way . First the unknowns , porting . It will absolutely need to be gone through and I plan on opening all ports to full bore diameter .25” . Magazine will need to be either sleeved to match the barrel or have a new wheel made to fit ( need measurements for possible 3D print) . Stock FPE is reported to be from 120 to 140 out of the box . The plan , turn the existing bolt down to .25 , modify the existing mag , install a TJ’s 257 liner in 1/2” OD . This sounds simple enough but the existing barrel is 9/16 so I’ll have to make a sleeve or new barrel adapter that threads into the receiver , then there is the shroud . I would like to install a 28” to 30” barrel which means I need to fabricate a new one . I don’t have the OD of the existing shroud but I plan on using carbon tube for weight . I’ll probably keep the existing stock , I like the looks of them and I already have enough tacticool rifles around . I’ve read RKR’s rainstorm tuning threads enough to get a good grasp of what I think I need to do . The barrel I’m using has already been tested for accuracy and have bonded a 15 mm OD carbon fibre tube to it . It is currently just over 31” . My FPE goal is 160 at 3000 psi which I think I can pull off with the barrel length I have in mind , and shoot a full 6 shot mag within 4%. I cant wait to get home to see my rifle ......... I mean wife and daughter . :P
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Ports in .357 Evanix are already slightly above 6mm so there's not much to do. Just smooth out the valve tunnel to TP turn, I believe it's already drilled at an angle in newer guns. Personally I'd consider making a new firing valve, stem without o-ring groove and the poppet smaller in diameter to make it easier to open. Then oval barrel port and hammer spring tuning and you should be at or close to your goal. You should also do something about the valve spring to keep it straight in the valve housing or remove it all together. Fixing the lower support for sidelever main screw is also a good idea.
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Evanix guns don't have a valve stem with Oring for some years now, was something they tried for a little bit and walked away from it.
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Thanks RKR , I’ve got the material for the lever bracket sitting on the bench at home already. I will probably turn down the poppet or make a new peek valve . Centering the valve spring I had forgotten about thanks for the reminder.
Manny do you know what the OD of the existing shroud is on theWinchester?
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Thanks RKR , I’ve got the material for the lever bracket sitting on the bench at home already. I will probably turn down the poppet or make a new peek valve . Centering the valve spring I had forgotten about thanks for the reminder.
Manny do you know what the OD of the existing shroud is on theWinchester?
Peek tends to leak below 140 bar, for a 200bar gun I would use PET-P/Ertalyte. The poppet has metal casing so it's better to make a new poppet or a new seal that extrudes a bit for the valve. Of course while you are at it I'd make a new stem also, I've seen a couple of mushroomed Evanix valve stems - they get stuck and you'll get a reservoir dump when shooting.
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Thanks RKR , I’ve got the material for the lever bracket sitting on the bench at home already. I will probably turn down the poppet or make a new peek valve . Centering the valve spring I had forgotten about thanks for the reminder.
Manny do you know what the OD of the existing shroud is on theWinchester?
Peek tends to leak below 140 bar, for a 200bar gun I would use PET-P/Ertalyte. The poppet has metal casing so it's better to make a new poppet or a new seal that extrudes a bit for the valve. Of course while you are at it I'd make a new stem also, I've seen a couple of mushroomed Evanix valve stems - they get stuck and you'll get a reservoir dump when shooting.
Thanks again , I didn’t know about the valve being difficult to machine . I do have a bit of PET to try and lots of drill steel stock for a new stem . Th fill pressure is suppose to be 230bar so I’ll be tuning from there . If you have any other bits of info I should need , I’m all ears .
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I meant the seal in the original poppet, it's just a thin disc of delrin. Timo has a trick procedure for heat treating the stem, perhaps he can contribute?
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No problem sealing with peek valve when it is correctly machined. Dont make the contact point too wide and it will hold just fine at about 50bar.
Drill rod is good material for the stem, no need for heat treatment if you go with hss rod.
Marko
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No problem sealing with peek valve when it is correctly machined. Dont make the contact point too wide and it will hold just fine at about 50bar.
Drill rod is good material for the stem, no need for heat treatment if you go with hss rod.
Marko
Any suggestions on the shape of the seat ? I’ve done a few and had pretty good luck with them . Would a slight taper into the bore of the passage help it seal? All the ones I’ve done so far have been straight cut. I’ve done disco and Hatsan BT65 poppets they’ve needed a good burnish with bore paste to get them to seal .
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Subscribed! Very interested in this.
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I agree, PEEK can work fine at lower pressures, if you keep the seat narrow.... 0.020" works well....
Bob
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You can use angled seat, anything up to 45 deg works. With peek and narrow seat it wont wedge too bad.
Marko
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That's good to know about PEEK. It should also require less force to knock the valve off the seat with thin sealing surface. Unfortunately the Evanix valve seat is not the best for that approach, it's like an o-ring slit in half horizontally. I tried PEEK poppet seal using original seat and seal forms and it started leaking when pressure got below 140 bar, an edge type poppet seal could have fixed that.
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Denis, the shroud on the Winchester is the same as the AR6
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Evanix .357 uses non backvented 25mm shroud, a cosmetic thing. Air space around the barrel is very limited so there's not much point in backventing it. If you want it quiet make a reflex type 2" LDC for the gun.
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Evanix .357 uses non backvented 25mm shroud, a cosmetic thing. Air space around the barrel is very limited so there's not much point in backventing it. If you want it quiet make a reflex type 2" LDC for the gun.
Cosmetic only in Canada . Don’t I wish I could quiet the rifles I have down . Thanks for the measurements .ill get a few lengths of carbon fiber on order.
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Well I made it home a few days early and my new Winchester was waiting for me . After a quick glance it appears to be well made with only a minor dent in the stock , probably from shipping . There wasn’t any air on the gauge so it’s either leaking or wasn’t charged to start with . What I havcan noticed is that there’s about three inches of dead space between the barrel and the end cap . Not sure what they were thinking as these couple of inches of extra barrel would definitely help to get a bit more power out of it . I don’t plan on shooting any .357 ammo through it , so I’m just going to start stripping it down . Pics and explanations will follow . ;)
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Cool, looking forward to plenty pictures.
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Alright , tore the rifle down , measured all porting at a full .25” from the valve through to the barrel . Inlet to the valve at .320” . That made it real easy . First was to remove the barrel , two set screws holding it on as mentioned before . Measured the OD so I could make a collar to fit over the .257” barrel. It ended up being at .630 “ so I turned down a piece of aluminium to the right OD , bored half of it out to fit a step down on the barrel because I had already sleeved the barrel with a carbon fibre tube . The barrel’s total length is at 31” . Once the collar was made , I used some more green locktite to secure the sleeve to the barrel . Installed the barrel into the action ,countersunk the holes for the setscrews ,drilled and prepped the barrel port to the full .25 “ ( actually .21”x.34” ) I had to make a tool for cutting the breech oring grove and cut it .125” from the breech end of the barrel. I then reassembled the rifle put the shroud on and you can see in the last pic how much longer the barrel is now . So far this project is super easy with the only machining is the sleeve and oring grove . Next on the list is to figure out what I’m going to do with the extra barrel sticking out past the shroud . Once that is done I’ll move on to sleeving the magazine and probably make a single shot tray for the much longer 257388 bullets I cast.
I did notice the hammer spring is quite long and has about 1/2” of preload on it . I’ll be taking care of that also . With the barrel length as is , I’m already thinking of getting a folding stock similar to what Manny did to his .
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Looks good so far, will be interesting to see the finished gun and what she can do.
Marko
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Today , I spent an hour or so making the adapt r between the existing shroud and a piece of aluminum tube far a fake suppressor to cover up the end of the barrel , the total length with 31” of barrel is 49” . It’s looking a bit like a Kentucky long rifle . That was the easy part. Now the magazine , I wasn’t anticipating it giving me so much grief . There’s a locating pin to Centre the next pellet as seen in the pic which means that dropping down to 25 cal , the bullets would be .050” off Centre . Not only that but the pin is internal requiring slots in the sleeves . So far I’ve got some test sleeves made out of plastic tubing and I fabricated a new stop pin bushing , I’ll take pics of it later once I get it all working . I’m getting close now but it will take a bit longer than planned , as per the usual.
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Maybe you can locate some of the Gen I .357 mags, it would make the conversion much easier.
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Why not start with the single shot tray, you will need it for long bullets anyway?
(https://farm5.staticflickr.com/4260/35774075725_37be3545c0_c.jpg) (https://flic.kr/p/Wveun4)ss-tray_zpsd55ecfc3 (https://flic.kr/p/Wveun4) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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Ok , I got the magazine working , I guess I just needed a break. I used some 3/8” OD synflex air line from my days as a hyghway truck mechanic cut lengths to clear the alignment pin . Pressed them into the bores so they were flush . Next was the alignment pin . For this I used a piece of brass tubing , I turned the OD so that it would have a .002” crush , then removed the material so that the profile matched the existing pin . Not the prettiest job , but it works . Put three full mags through the gun on a single fill . Not sure what the velocity is as this was just a function test. So far so good , no irreversible mods done to the rifle or magazines , next is tuning and to make a single shot tray . There a pic of the assembled rifle with my BT65 for comparison . I’ll also be mounting my Athlon BTR on this rifle as it’s purpose will be 100 yards or more. I should also mention that I filled the gun using my Hatsan probe as it was already set up . One more big plus for the Winchester/Evanix .
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Cool project. I really like the concept of buying a gun designed for a large projectile and downsizing the barrel/probe. Should be a fairly straightforward project. Usually we are all going the opposite way and trying to get more out of less, which in many cases is like trying to push a rope.....
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Initial chrony testing done . Filled to 230 bar , shot two mags over the chrony , start at 790fps and ending at 845 FPS on the twelfth shot with 190 bar left . Looks like my porting is spot on and I just need to add some spring to get it where I want . This was done with the factory spring and adjuster flush with the receiver . I have a good assortment of springs and I think I found a combo for a short twin set up with no preload . I did however forget to order some 30mm rings . Sure wish they had cut the picatinny slots in the receiver . Amazon should have some medium / high rings that will have to be rushed in .
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Initial chrony testing done . Filled to 230 bar , shot two mags over the chrony , start at 790fps and ending at 845 FPS on the twelfth shot with 190 bar left . Looks like my porting is spot on and I just need to add some spring to get it where I want . This was done with the factory spring and adjuster flush with the receiver . I have a good assortment of springs and I think I found a combo for a short twin set up with no preload . I did however forget to order some 30mm rings . Sure wish they had cut the picatinny slots in the receiver . Amazon should have some medium / high rings that will have to be rushed in .
What's your bullet weight? It sounds a bit like the valve housing inlet is restricting your power curve. Although reducing it is a PITA so it would be better to start with valve spring first.
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THIS is cool, and I'm commenting just keep up with the thread. I really like the idea here!
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I guess I forgot to add the bullet weight, 70 grain from a 257420 arsenal mould. The stock spring is pretty weak , if the new spring doesn’t work I’ll be making a peek valve and open up the valve inlet. I haven’t touched the porting at all yet . This is as it comes from factory , all straight cut .
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I guess I forgot to add the bullet weight, 70 grain from a 257420 arsenal mould. The stock spring is pretty weak , if the new spring doesn’t work I’ll be making a peek valve and open up the valve inlet. I haven’t touched the porting at all yet . This is as it comes from factory , all straight cut .
So there was no 45 degree drilling from valve tunnel to valve housing exit? If that's the case you should round up the corner there as good as possible, you should gain some 30-40 fps.
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I’ll be doing some tuning in the very near future and expect to have some much better results . If porting is straight cut as I presumed , this will be fixed for sure.
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I found a heavier spring ,cut it so that when the adjuster was flush it had 1/8” of gap . Ran another two mags over the chrony . Starting at 230 bar again with the same 70 grain bullets . First shot at 890 FPS so I knew it helped . The following 11 shots had an ES of less than 20 FPS and ended at the same 190 bar .it was almost like shooting a regulated gun only at 125 FPE . I’m sure I could get another mag as the peak was on my last shot at 910 FPS . I’ll do some accuracy testing and that should tell me if I should increase the hammer tension or leave it as is . So far color me impressed , this was one of the easiest conversions I’ve done to date . Putting the numbers in Lloyd’s efficiency calculator the rifle is at 1.87 FPE/ci, those are the best numbers I’ve ever done even with my low powered .22 disco build . That 31” barrel must be the reason . :D
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I found a heavier spring ,cut it so that when the adjuster was flush it had 1/8” of gap . Ran another two mags over the chrony . Starting at 230 bar again with the same 70 grain bullets . First shot at 890 FPS so I knew it helped . The following 11 shots had an ES of less than 20 FPS and ended at the same 190 bar .it was almost like shooting a regulated gun only at 125 FPE . I’m sure I could get another mag as the peak was on my last shot at 910 FPS . I’ll do some accuracy testing and that should tell me if I should increase the hammer tension or leave it as is . So far color me impressed , this was one of the easiest conversions I’ve done to date . Putting the numbers in Lloyd’s efficiency calculator the rifle is at 1.87 FPE/ci, those are the best numbers I’ve ever done even with my low powered .22 disco build . That 31” barrel must be the reason . :D
SSS with negative preload kills most of the hammer bounce, if not all as seems to be the case here. Opening up the valve housing inlet should net you some more fps at higher pressure, but then again 910fps might well be the sweetspot for accuracy making it unnecessary. Have you considered adding a regulator, that should give you groups with single figure fps spread. Good job there, it will be interesting to see some accuracy results from the gun.
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With that kind of efficiency, you are leaving quite a bit of power on the table.... Try it at 1/16" of gap and see what happens.... What is the reservoir volume?....
Bob
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Bob , the reservoir is supposed to be 320cc according to the Winchester manual , though I’ve read 300cc from the Evanix website for the Blizzard.
RKR , I might revisit the porting once I test with the heavier 85 grain ammo . For now I still have preload to use and I haven’t maxed out the spring to see what it will do with the existing porting .
To date there has only been one permanent mod done . I reduced the diameter of the probe to .25” . I have placed an order with PA for a replacement , this way I can change back to a .357 which should take less than 10 minutes . One last thing , I’m going to put it in an ATI 10/22 stock as per Manny’s method . This should save me a bit on length for the bush whacking .
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WOW !! ...that was fast :)
The reservoir is 300 cc
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Tried the hammer adjustment at full coil bind and only gained 5 fps . Looks like RKR was spot on and I have some porting to do . Kinda doesn’t make sense to me as the efficiency was stellar . Oh well . Managed to get the valve taken apart , made a peek poppet and reduced the OD from .435” to .380” . The stem is a little big at .162” but I will take it down some close to .125” . I did notice I didn’t turn down the section of the pellet probe at all and it is at .159” . Which is way too big for a .25 cal bore .
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Wait a minute.... You went from a 1/8" spring gap and 890 fps to full coil bind at 895 fps at 230 bar.... and yet the gun shoots 910 fps at 190 bar?....
Does not compute.... ???
Bob
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Wait a minute.... You went from a 1/8" spring gap and 890 fps to full coil bind at 895 fps at 230 bar.... and yet the gun shoots 910 fps at 190 bar?....
Does not compute.... ???
Bob
Sounds to me like he just didn't have enough spring strength to crack the valve at 230 bar. I wonder if his first numbers were with the adjuster flush, or he was just mentioning that as a reference to note his spring length? I'm sure that will change with the PEEK poppet though.
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Your results sound similar to my .357 experiences. With stock valve housing inlet I got this:
200 bar with JSBs
822 fps (first shot after tune, I guess it's OK to be low)
860 fps
870 fps
865 fps
862 fps
866 fps
866 fps
840 fps
827 fps
816 fps
130 bar
And after opening it up to 9mm I got this:
200 bar, 88 grain bullets
904 fps - 160 fpe
904 fps
897 fps
880 fps
861 fps - 150 bar
836 fps
817 fps
804 fps - 125 bar
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Bob ,at full coil bind the second string was near identical only I gained 5 FPS at the peak. I think I only gained dwell time which did basically nothing due to restriction in flow.
RKR , none of the ports are beveled or cut at a 90*. Also the valve stem has a grove cut for an Oring like the older models .
I’ll take some pics of the new parts I’ve and the porting . They sure don’t leave a lot of room in there for opening up the valve inlet. I have an idea but not sure if it will work out as planned . We’ll have to see later on today.
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Bob ,at full coil bind the second string was near identical only I gained 5 FPS at the peak. I think I only gained dwell time which did basically nothing due to restriction in flow.
Well, my friend, you have run into a situation I have NEVER seen before in a PCP.... You mean the entire curve moved up 5 fps from beginning to end?.... What SHOULD have happened is that your curve should change from
890 fps @ 230 bar - 910 fps @ 190 bar
to, as an example....
930 fps or more at 230 bar - 910 fps or more at 190 bar
The fact that you are getting less velocity at 230 bar than at 190 bar indicates that you have insufficient hammer strike to get the dwell needed at 230 bar to max. out the velocity.... ie the valve is closing before the pellet reaches the muzzle (partial valve lock).... That may or may not be the case at 190 bar, however, as the velocity may already be maxed out at that pressure.... When you increase the dwell by hitting the valve harder, at 230 bar it will open faster and further, and stay open longer.... That additional dwell will increase the velocity at 230 bar.... regardless of port size....
If this is not occurring, you have the first PCP I have ever heard of that produces more power at 190 bar than at 230 bar, when the gun is maxed out so that the valve stays open until the pellet leaves the muzzle.... I just don't see how that is possible, given the laws of physics.... The port size is the same in both cases, so more pressure must mean more power, providing the hammer strike is sufficient to keep the valve open long enough....
It is possible that there is a hammer stop on the back of the valve (some Korean guns had them, and they were even adjustable)…. and that the hammer is rebounding off that stop before the valve opens more than a small amount?.... I don't even know if that could cause the problem, but otherwise I got nutthin'....
Bob
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So after too many hours of trying to figure out why my shot strings weren’t consistent . It came down to the chrony . I cleaned up the porting , got the valve inlet bored out , made a spring centering cross like RKR (only I tapered the leading edge :P ) , replaced my breach o ring and reworked the leade in . I’d have one sting starting at 750 FPS the next at just over 900 with no changes . After changing the battery in the chrony , the numbers are a consistent starting at 850 up to 950 back down to 830 in two mags . That’s at near coil bind . The spring isn’t strong enough and the double spring setup I wanted to use went missing . I’m peaking at near 200 bar from a 230 bar fill . I knew .187 for efficiency was way too good to be true. There’s a lot more power available on tap yet . Now to go spring shopping.
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The good news is that you have all the power you need for that bullet weight.... By the time you add a bit more spring to get the string so that your ES is about 4%, I'm guessing that string will be about 930-970-930 or a bit faster, over 1 mag. or a bit more.... Alternately, you could drop your fill pressure a bit until your first shot is ~ 912 fps, shoot to the peak at 950, and then back down to that velocity to get within that 4% ES.... That would still be pretty decent performance, and with a lower pressure fill you would get more fills per tank.... It would be good to know how many shots you can get within a 4% ES anyways, as that is a good goal for a 50 yard gun.... If you want to stretch that to 100 yards, I would recommend you try and get the ES down to 2%....
I see you plan on using a heavier bullet, so all the above will apply, just at a higher pressure (or bigger ports) to get the same velocity with a heavier bullet (more FPE)…. Yes, you will definitely need a stronger spring to increase the dwell for a heavier bullet....
Bob
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Got the gun tuned to the point where it’s shooting a consistent 6 shots from 920 to 950 back to 930 . I’m going to try a find a better spring , would like to use a free flight hammer but not sure it’s doable at this power level . I reworked my trigger sear a bit to gain some first stage by putting a tapper on the contact area , also trimmed a few coils from the sear spring . With now we’ll over 100 shots over the chrony , glad to say there have been no mechanical issues . I really like the way Evanix uses the mono block design . Can’t wait to try this rifle at the range ,hopefully in the morning before the rain starts .
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First time at the range and boy am I happy . I’ll try to up my status on the NUAH with this one. All shot at the same range 104 yards lazered . If I can get my ES down a tad I’m sure I could even improve the groups . Pics of my setup and targets so you can see I’m not cherry picking . Some of the targets were sight Ins after mounting my scope. I through in a pic of the Win hanging with its .25 cal friends .
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nice work. Loved following this projeCT I learned a great deal about tweaking shot strings and springs valves and what a shot string can tell you about what the internal mechanics of the hun are doing. great shooting. Keep it up!
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Thanks Tim ,
I still have a few things I’d like to try . Thinking of adding some weight to the hammer and going to free flight . As of now there a good amount of hammer bounce that is like to get rid of . That and I haven’t shot any of the heavier ammo yet .
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Here's a photo of a newer style stock Blizzard .357 valve parts.
(https://farm2.staticflickr.com/1861/29841134687_6376e8d7e4_b.jpg) (https://flic.kr/p/MsXBGc)evanix-valve-housing (https://flic.kr/p/MsXBGc) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
As you can see the valve housing exit hole is drilled at an angle and poorly so as it almost touches the o-ring on one side. For a .257 it would be a good idea to oval the exit hole so it sits in the middle of those o-rings and then redrill it through with a 6.5mm drill bit. Due to the angled drilling the air flow is much better than it was in the old style valve block so I don't think additional porting would provide much extra flow. The weak bit of the actual firing valve is the o-ring groove where the 4mm stem is only 3mm in diameter, that's where these stems usually snap in half. Another problematic spot is the Delrin (or whatever soft plastic they use) seal on the poppet. It is encased by that metal poppet and as you can see this one (from a gun that was never shot) is already compressed quite a lot almost down to the poppet's metal cup. After some shooting it compresses even more and the metal will take contact with the seat causing a leak to develop. A proper fix for this would be to make a new firing valve, I'd use 4mm HSS drill bit for the stem and make the poppet entirely from PEEK with sharp edges and 8.3-8.5mm diameter to meet the 7.5mm valve tunnel. Any better ideas or further improvements to suggest? How much larger than valve tunnel PEEK poppet do we actually need?
Edit, here's the valve seat design:
(https://farm2.staticflickr.com/1841/44058874484_1c2124720f_b.jpg) (https://flic.kr/p/2a8kfoY)evanix-valve-seat (https://flic.kr/p/2a8kfoY) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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I’m presently working on getting my 10\22 stock prepped and the action sitting in it . I’m getting close . Once it’s done I’ll probably revisit the valve . I have enough power on tap , just need to work on the efficiency . I’ll post a pic of the stock once complete. I’m also contemplating milling a few slots for the scope rail. Not sure what they were thinking as standard picatinny scope mounts don’t work .
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Finished up the stock and cut some groves in the action to fit some FX no limit rings . Now it’s ready to go hunting .
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Finished up the stock and cut some groves in the action to fit some FX no limit rings . Now it’s ready to go hunting .
That looks wonderful Denis! That is going to make one heck of a hunter right there ;)
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Very nice!
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What I really wanted to use was a factory Rainstorm thumbhole stock . Unfortunately they are impossible to get. I’ll be on Holliday’s for the next week so I intend on doing a lot of shooting .
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Another video of some hammer bounce. https://youtu.be/n4p7X7_Lnn8
I have to get rid of this , at least two extra valve openings happening here . More Cobra tech anyone ?
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With stiff double spring combo and a tad negative preload I managed to reduce the bounce to one small extra opening in my .357. The power was somewhere around 130-150 fpe at that point. I've tried several HDD versions in my gun but none has worked with the forces involved.
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I’ve been trying a couple different spring combos but my velocity is way too slow at 190 bar . I’ll get there just need to play with it a bit more . Still trying to figure how to incorporate a cobra cylinder . Hope To see JSAR make an SS valve . That would kill two birds at once .
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I’ve been trying a couple different spring combos but my velocity is way too slow at 190 bar . I’ll get there just need to play with it a bit more . Still trying to figure how to incorporate a cobra cylinder . Hope To see JSAR make an SS valve . That would kill two birds at once .
That IS going to happen and soon!
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Fantastic Travis , count me in for a valve . If you need a beta tester , I can do that too. Just let me know what needs to happen .
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Any room to fit an SSG in there?....
Bob
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Any room to fit an SSG in there?....
Bob
It should be doable if you hollow out the spring guide in the rear plug. Will it hold out is then another story.
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After a few hours attempting to make an SSG that worked I gave up. There just isn’t enough room in there for the amount of power I’m trying to make . Not to mention the fairly lightweight hammer . I did however set the factory spring ( lost nearly 3/4”)and retunned the gun for a 230 bar fill . One full mag all over 130 FPE with an ES of less than 40 FPS . Coyotes beware , not to mention the raccoons that have been raiding the neighborhood bird feeders .
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Got the gun tuned to the point where it’s shooting a consistent 6 shots from 920 to 950 back to 930 . I’m going to try a find a better spring , would like to use a free flight hammer but not sure it’s doable at this power level . I reworked my trigger sear a bit to gain some first stage by putting a tapper on the contact area , also trimmed a few coils from the sear spring . With now we’ll over 100 shots over the chrony , glad to say there have been no mechanical issues . I really like the way Evanix uses the mono block design . Can’t wait to try this rifle at the range ,hopefully in the morning before the rain starts .
Hobbyman, any ideas what speed you got at around 185 bar? I gave it a go by putting a .257 barrel in to my Blizzard and first test shots with 257420s were at around 930 fps when shooting at 185 bar tethered (~140 fpe). The tune is roughly the same that provided 230+ fpe in .357 so this seems a bit low to me.
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Actually, that result is about what I would expect.... If the .357 had full bore-area porting and was producing 230 FPE like that.... then in .257 cal you would expect about (.257^2 / .357^2) x 230 = 119 FPE at the same pressure, with the same barrel length.... If the porting was .257 throughout, then it would be ideal in .257 but fairly small for a .357.... so the calculation becomes influenced by the restriction suffered by the larger caliber.... In this case a reasonable approximation for maximum FPE may be made by using (.257 / .357) x 230 = 166 FPE.... Both of these calculations are for a "dump shot" where the valve is open until the pellet exits the muzzle.... Your result is right in the middle between those two numbers, which would be pretty typical for a "real" PCP where you changed calibers, in my experience....
Bob
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There's an edge going from transfer port to barrel port, I'll try fixing that and it may net me some 10-20 fps. Other than that it's pretty much there.
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Sounds like you got it figured out pretty good RKR. I was able to get higher FPE by adding more hammer spring but the shot count went down as expected . I was after a full mag . If I was shooting tethered to a regulated tank I’d start at 220 bar and crank the hammer spring to coil bind . I’m sure 150 FPE is doable with such a long barrel.
Any pics of your build ?
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Sounds like you got it figured out pretty good RKR. I was able to get higher FPE by adding more hammer spring but the shot count went down as expected . I was after a full mag . If I was shooting tethered to a regulated tank I’d start at 220 bar and crank the hammer spring to coil bind . I’m sure 150 FPE is doable with such a long barrel.
Any pics of your build ?
I think I can get at or close to 150 fpe. The gun is apart now to fix some small things but I'll take some photos once it's back together. I got this power with stiff double spring combo and as much positive preload as possible. There's some extra weight in the hammer as well for longer valve dwell. 5 shots went from 185 bar down to 150 bar, unfortunately the chrony acted up so I missed 3 speed readings there. In addition to better transfer to barrel port transition I could make a smaller diameter PEEK poppet and use longer valve stem for more power but I'll see if porting alone gets me up to the 150 fpe level. I could also give the original hammer spring a go to see what happens.
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Well then, fixed the barrel port, shortened the pellet probe nose a bit and attached an adapter at the barrel end which allows me to screw in a A&M Marksman. With Marksman I was able to ditch the earplugs and use my Combro which is far more reliable than Chrony. 257420s were clocking at 960+ fps putting me at around 150 fpe. 388s shot at 860 fps, all shots at 180-185 bar. I think that's good enough for me. Photos next.
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This is how it looks. That scope is there just for the photo, I need to buy a proper one for this gun. I've been thinking about a Sightron SII with fixed 36x mag, any opinions about that?
(https://farm5.staticflickr.com/4900/43976548380_f51f97197b_k.jpg)
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I really like those Blizzard stocks , sure wish Winchester had done a better job . RKR, your mag well sure looks to be the same width as the new models . You might be able to use one of the newer style mags . I thinks the new ones are , just over .84” . At 36x what kind of FOV do you get at say 100 yards ?
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I really like those Blizzard stocks , sure wish Winchester had done a better job . RKR, your mag well sure looks to be the same width as the new models . You might be able to use one of the newer style mags . I thinks the new ones are , just over .84” . At 36x what kind of FOV do you get at say 100 yards ?
I kind of like the Winchester stock, reminds me of old centerfires. Magazine well is 19mm long so about 0.75", Winchester mags are not going to fit in there. At 36x mag the FOV should be about one yard at 100 yards which is OK for paper punching. I've been debating whether I really need lower mags or not, sometimes it would be nice to tune down the mag and shoot targets at different distances with mildots.
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I’m using a 6x24 and at 100 yards the holes are pretty clear at full mag. While hunting though the site picture just isn’t wide enough and I usually drop to 16 or 18x at 100. That reminds me I’ve been looking for a throw lever for the mag ring on that scope .
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For hunting with a .257 I'd be very tempted to use one of these Hawke scopes: https://us.hawkeoptics.com/vantage-4-12x50-rimfire-22-subsonic.html (https://us.hawkeoptics.com/vantage-4-12x50-rimfire-22-subsonic.html) I have one in my 10/22 and it's great for hunting. If you turn down the mag a bit it should fit the trajectory of a .257 bullet travelling at 950 fps. Combine with scope mounted range finder from these guys and all you need to do is to read the wind correctly http://customriflescopes.com/shop.html (http://customriflescopes.com/shop.html)
I plan on shooting at 200M also and maybe even further, thus the want for good optics and enough magnification.
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Did some more tuning for a new bullet mold . Got a dual spring setup and from a 220 bar fill I’m shooting 63 grain cast from 880fps to 910 fps back to 870 over two 6 shot mags . With a simple spring change can go back to slinging the 257420 to 950 fps . Pretty happy with this set up , really happy with the overall performance of the rifle in .257 cal . To see what these bullets are capable of check https://www.gatewaytoairguns.org/GTA/index.php?topic=151263.0. (https://www.gatewaytoairguns.org/GTA/index.php?topic=151263.0.)
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Snow is slowly melting and I finally managed to score a proper scope so it was time to zero the gun in my garage. To my surprise it was blowing air out of the magazine well and speed was rather erratic so I went to change the o-ring for the barrel. Now this didn't fix the problem entirely but I managed to get up to 1040 fps with 257420 boat tails, that's 170 fpe so it seems I've been missing some power. Anyway, the problem is the CF tube that I used to fit the barrel to the breech, it has blown out the epoxy in between the barrel port and breech end of the barrel :'( I need to figure out how to fix that, it seems that 13mm ID CF tube around a 12.7mm barrel is not going to work.
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The barrel sleeve I made was from a press fit aluminium tube . That’s some pretty good power , nice going . I’ve been thinking of a bottle conversion for this gun . I’m going to have to talk to Travis at JSAR about a bottle adapter and short tube .
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Now that sounds like a plan! 8)
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Made a copper sleeve for the barrel (a real PITA to make without lathe or reamer) and no more blowby at the breech. However, the gun is now shooting single digits in the middle of the 920 fps where it was set before. I'm rather puzzled now, how can a blowby at the breech cause the speed to jump over 100 fps? There could be a small alignment difference at the barrel port but that is still a LOT of difference and hard to explain by that alone.
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Not sure I understand , “single digits “ . Are you saying the velocity dropped to the md 800’s ?
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Not sure I understand , “single digits “ . Are you saying the velocity dropped to the md 800’s ?
Sorry, no - I say I'm seeing ES of single digits averaging 925 fps (923-928 when tested for a few shots) - just where the gun was set last autumn. I just wonder why the leak caused me too see much higher and also lower numbers. Could it be that the valve is closing slower due to the leak?
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Leakage absolutely kills efficiency and accuracy most times it’s reared it’s ugly head on any of my rifles . Ive had a nicked Oring on my Frankengun that caused wild ES issues and that in turn gave me poor accuracy . What was odd is that it would shoot great over the chrony indoors with a stable spread but as soon as I would take it out to the range my poi was all over the place . I finally brought the chrony to the range and that’s when I saw the 120 - 140 fps spread within a couple of shots .
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Leakage absolutely kills efficiency and accuracy most times it’s reared it’s ugly head on any of my rifles . Ive had a nicked Oring on my Frankengun that caused wild ES issues and that in turn gave me poor accuracy . What was odd is that it would shoot great over the chrony indoors with a stable spread but as soon as I would take it out to the range my poi was all over the place . I finally brought the chrony to the range and that’s when I saw the 120 - 140 fps spread within a couple of shots .
Leak in barrel/probe o-ring should reduce the power and cause poor ES. That 115 fps over the normal reading (got some more in the 1000 fps range) makes me wonder what all is going on in the gun during a shot.
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Are you getting over 1000 fps with the 257420? If so that s pretty impressive . I’m not real big on math and calculating what goes on in the rifle itself . Testing and tuning is relaxing for me . Best I could do is guesstimate what is going on .
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Well the barrel port was misaligned. After fixing that the 257420s are flying in between 980-990 fps, 157 fpe. I was hoping a bit more but I guess I can live with that. Now I'm wondering if I could repeat that 1040 fps ...
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RKR , very impressive for a knock open valve with a long transfer path . I don’t think there’s much more available power wise . Have you by chance polished the inside of the TJ’s barrel ? I picked up nearly 30 FPS after polishing with the same bullets and settings . Good work .
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RKR , very impressive for a knock open valve with a long transfer path . I don’t think there’s much more available power wise . Have you by chance polished the inside of the TJ’s barrel ? I picked up nearly 30 FPS after polishing with the same bullets and settings . Good work .
Polishing barrel was the first thing I did. Barrel snake, autosol and 50 pulls through. Made a big difference in smoothness when you push through a bullet.
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Still not fire lapping I see? With boresnake and autosol you are just rounding off the lands and doing next to nothing to the problem areas at the groove corners.
Marko
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Still not fire lapping I see? With boresnake and autosol you are just rounding off the lands and doing next to nothing to the problem areas at the groove corners.
Marko
I might firelap later if needed. As it is the barrel felt rough when slugging with a bullet and it went to a smooth push through after polish. It's not mirror polished but I believe the cleaning interval should be much longer and that was the main point of the polish job. Now I need to get it to the range to see if it's accurate.
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I finally managed to shoot some groups, I was very limited on time so it was one or two 5 shot groups / bullet size. The 257420s I cast myself all turned out under sized and groups were over an inch. The best one was 257420 BTs cast by Teemu and IMO even those could be a tad bigger - pulled one shot and there was a moderate side wind that I completely ignored to get some shooting done before sunset:
(https://live.staticflickr.com/65535/47687045892_8f4da156a2_c.jpg) (https://flic.kr/p/2fDWzmq)257420bt (https://flic.kr/p/2fDWzmq) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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That is some good shooting even with the pulled shot . Have you tried adding a bit of tin to the lead mix ? It might help getting the bullets to cast a bit bigger . If that doesn’t work I’ve heard spinning a bullet with JB paste in the mold opens up the cavities a few thou without damaging the mold .
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That is some good shooting even with the pulled shot . Have you tried adding a bit of tin to the lead mix ? It might help getting the bullets to cast a bit bigger . If that doesn’t work I’ve heard spinning a bullet with JB paste in the mold opens up the cavities a few thou without damaging the mold .
I did enlarge one .224 mold using that bullet spin technique and it worked, although I had to size down my bullets after that. My 257420 mold is 4 cavity so I'm rather hesitant to do that, getting all cavities to drop the same would be a PITA. I don't have .257 sizing dies either so I've been trying to work with lead mixtures, I may give a 2% tin mixture a go next.
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Also, try higher pot temp. As the temp goes up, the dia. of the bullets does as well.
However, higher heat separates tin from the mix, so lead only for the test of higher heat. I like 850 to 890 for larger dia. as cast bullets.
Mike
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I sorted out the bullet size problem by beagling the mold. It now drops slightly over bore size with wheel weight lead so I had to make a .257 sizing die as well. A 10$ part that ends up costing 60$ when shipped to Europe >:( I was making some changes to the barrel band and decided to slug the barrel while it was off the gun, this is the lead build up after hundred or so shots:
(https://live.staticflickr.com/65535/47034083844_83b2726eb9_c.jpg) (https://flic.kr/p/2eEeYu5)lead-buildup (https://flic.kr/p/2eEeYu5) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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Wow , that’s a lot of lead buildup . Glad you got your mold worked out . I got quite a few sizing does from NOE and yes they are a bit expensive when you factor in the shipping . I usually wait til I have a decent sized order before hitting the buy button . I have made my own but took me nearly three hours , not really worth it time wise .
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One more time do you think autosol and tampon string works, did I mention something about fire lapping.
Marko
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One more time do you think autosol and tampon string works, did I mention something about fire lapping.
Marko
It works to a degree, now I know what degree it is. I'll do the firelapping next now that I have bullets, was it hard or soft bullets that work best?
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As hard as you can get with lead and antimony.
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When I casted fire lapping bullets I put pile of pellets, 5% Sn, single letters ( foudry type ) and some wierd lead which has unknown hardness but it was not pure. Those bullets where something like way over 20 BHN. And worked very well with wheeler bore lapping kit grits. Fire lapped Corsair's barrel on that alloy and it is working well...
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I would need to lap the fury barrel but that would take too much lead and couple of wheeler kits. :o
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I would need to lap the fury barrel but that would take too much lead and couple of wheeler kits. :o
;D
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I did some firelapping, 5 + 5 + 15 shots with 240 to 600 grit paste. No difference in bore size and it looks like the bore is still a bit rough, I guess I should do another round of firelapping.
(https://live.staticflickr.com/65535/47802358942_973bf1c081_c.jpg) (https://flic.kr/p/2fQ8zUs)f-lapped (https://flic.kr/p/2fQ8zUs) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
I ran out of air so need to get the bottle filled before I can continue. I also ordered a borescope from ebay, should give me better idea of the bore smoothness.
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Holly cow that is horrible!
How did you apply the paste?
Marko
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Holly cow that is horrible!
How did you apply the paste?
Marko
Applied a glob of paste on a steel plate, dropped bullet on paste and rolled it in between two steel plates a couple of times until the grooves were filled with paste. The barrel looked and felt much worse before I polished it.
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Much worse than that and I would have made bushings or something else of the barrel.
Or sent it back to where it came from if sold as new.
No need to roll between plates, just smear it on the bullets so that there is plenty of compound and shoot. Start with coarse and shoot some 10-20 of those on a barrel that horrible. Good thorough cleaning and next grit 10-20 shots.
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I’m not 100% certain if that is indeed the barrel RKR got from me . I can assure you 100% that the one I sent him was a brand new TJ’s barrel liner with only the leade cut using a proper bearing piloted reamer from a known manufacturer. From the pic it sure looks a lot rougher than the other three barrels I had shipped to me at the same time and I’m asuming from the same batch . If it is the same barrel , the TJ’s liners and hammer forged and I have no idea how you would get a rough finish using that process.
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I got Corsair. 308 like 6 years ago from other fellow here in Finland and barrel is TJ's and it was very rough. I ask friend (TPL) how to proceed and he gave me instructions on fire lapping. I casted hard cast bullets and shoot 15 x 220 grit and cleaned in every 5 shot. Then 15 x 320 grit same cleaning and then finnished with 600 grit 20 shot if I remember correctly.(wheeler lapping kit) Well rest is history, rkr and other fellows from Finland knows how that gun shoots. ;D Better than owner can shoot...
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Double post sorry.
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That's the barrel I got from you Hobbyman. The camera on my mobile affects things, it does not look all that bad with naked eye. Although I did check my Peurala barrel with the same camera and it did look smoother, so more firelapping needed.
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I opened my Marksman for cleaning after the firelapping session, it seems that the stock internals can't quite take 150 fpe:
(https://live.staticflickr.com/65535/47071388624_29d03d391c_c.jpg) (https://flic.kr/p/2eHxaTW)marksman (https://flic.kr/p/2eHxaTW) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
The frontmost steel "curler" had turned in to accordion causing baffle misalignment and clipping on plastic baffles. I need to make better internals for it.
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Do not let the grit fill the lube groves in the bullet. It will only be grinding the barrel very inconsistently. Roll between two steel plates and imbed the grit in the walls, or driving bands only.
Once finished, I like like to follow with bullets rolled in damarious earth (ultra fine grade) and fire lap with it. It is the same thing JB bore pasted is mader from and will polish the barrel.
I finish this with using a mop or very tight patch with Flitz polish on it. The barrels come out like a mirror and time to recrown. ;)
Make doubly sure you wipe all the grit out of the lube grouves. Always! the point is to very finely lap the barrel rather than grind it. :o
Knife/Mike
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The .257 entered it's first 100M BR comp and managed to take second place, this was mainly due to the problems others had and I also had a serious vertical spread problem with my groups. After the comp I put chrono on and noticed occasional velocity drops up to 30 fps! Dang, no wonder I had those low shooting fliers.
So, the gun went to pieces and I started looking for the problem. I went through the hammer system checked tolerances and made rear centering guide for the springs, no help there. As I did not have this problem when the gun had .357 barrel I started browsing through my old tuning notes and there was one major difference, when I had the gun tuned for high power I had dropped off the valve spring which I had now in place. So, off comes the valve spring and gun gets assembled once again. Problem found, bullet speed jumped up some 20 fps and velocity spread is now about 3 fps (m/s conversions). It looks like the stock Evanix valve spring is seriously hurting the air flow and at high power levels it also causes a huge fps spread. So, for you other Evanix tuners - see how it does when you remove the valve spring.
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Congrats on the second place finish. By the sounds of it you got the barrel shooting well. That’s some good info on the valve spring . I haven’t shot mine in a while since my last purchase but will be taking it out soon enough. I don’t even remember what I did with the valve right now . Might be time to revisit that one .
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A huge congrats Ric! 8)
Yep, I looked at your method of using a cross piece to anchor the valve return spring. Nope, ditched it altogether and really opened the passage/ about .75" of open. LOL but she is running a Huma at 165 bar.
Mike
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I'm running Huma tethering regulator at 185 bar and I have 10mm hole feeding the valve chamber. 19mm hole is huge, or did you mean 75% of the 14mm indention there?
The cross type spring holder was starting to hurt after few hundred shots and would eventually disintegrate so I ditched it. Not such a good idea as it seemed to be :(
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I'm trying remember. it is exactly the same ida. as the interior of the valve body.
Just checked. It's 13mm. ;)
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200M BR done, I learned that the barrel still lead up real quick - the second group spread out of target paper as velocity was dropping due to clogged up barrel :( However, after cleaning up the barrel I managed to shoot this group at 100M with 257420BTs:
(https://live.staticflickr.com/65535/48271717607_7b629d137d_b.jpg) (https://flic.kr/p/2gxBaTe)100m-group (https://flic.kr/p/2gxBaTe) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
257388s do real small horizontal spread but vertical is huge for some reason. More work needed for the gun but it's starting look rather promising.
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Ric, have you fire lapped and polished the bore yet?
Mike
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Ric, have you fire lapped and polished the bore yet?
Mike
I did light firelapping but obviously it wasn't enough. I guess I need to get the Wheeler kit, once I find someone here in Europe who sells them.
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Once I finished fire lapping, I mixed up a batch of diatomaceous earth and light oil and fire lapped wit it. Virtually the same as jb bore polish. Ended up with the German Flitz Metal Polish and polished with patches or bore mops. And finally re-crowned. Can go 250-300 rounds without a cleaning now at full power in the .257, and over 500 with the lower power .25 slug shooter. ;)
The bore is a smooth, almost complete mirror finish. I use strictly 10 wt silicone RC shock oil on the bullets. Really helps accuracy a lot! 8)
Mike
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Risky that sure looks like a great group . As for the 388 bullets . I would weigh them , if they are from the batch I sent you. They were not exactly my best cast. I’m still learning . Did I mention how much I love the .257 caliber . By far my favorite , I thinks it’s the standard all others should be judged by. Not to mention , power and efficiency are a very good balance .
If you haven’t already , give the JSB king heavies MKII in that barrel . They might surprise you. I’m looking into modifying the hammer spring adjuster on mine . Possibly changing to a coarser thread and having a thumb wheel to be able to adjust on the fly without removing the stock.
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I’m looking into modifying the hammer spring adjuster on mine . Possibly changing to a coarser thread and having a thumb wheel to be able to adjust on the fly without removing the stock.
Something like this?
(https://live.staticflickr.com/65535/48274051962_fe11420ea5_z.jpg) (https://flic.kr/p/2gxP8NJ)power-adjuster (https://flic.kr/p/2gxP8NJ) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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I got a new tethering regulator and decided to play a bit with pressure, at 210 bar the 257420s were going out at 1030 fps or 170 fpe. That's pretty good for Evanix platform and getting close to the level of Air force guns. I also added a second CF sleeve for a barrel and a hamster :) Our next comp is 100M from standing position, I guess the gun is now ready for that but I don't know about me.
(https://live.staticflickr.com/65535/48486223027_c9992f9402_b.jpg)
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That’s some pretty impressive power Riku. I like what you did with the Hamster I don’t shoot in any type of competitive manner whatsoever , but it looks like your rig is ready.
I was out with mine last week and noticed that my velocity would drop whenever I adjusted to give more hammer spring . I’m pretty sure I’ll have to look at my valve return spring .i really need to find a better solution for the airpath through the valve .
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Denis, if you figure out a smart way to keep the flow and valve spring let me know. I did experiment with a stiff single hammer spring (12mm OD, 1.8mm wire) and while it worked with 257420 bullets it gave poor performance with 257388s. I ordered a similar spring made of 2mm wire to see if that would work.
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Some more testing with 257388s, they reach a velocity plateau at around 180 bar peaking at only 144 fpe / 870 fps. That is rather disappointing as they only weigh 12 grains more than 257420s and those lighter bullets still went 30 fps faster from 200 to 210 bar topping at 170 fpe. I wonder if more striker energy would allow for more power with these heavier bullets, after all they do have a very good BC so it would be nice to be able to use them as well?
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Riku,
It sure sounds like you need more hammer weight or more spring . Surely you’ll have it worked out . I shared a couple PM’s with Knifemaker and he told me he’s been running with no valve spring for some time . I’m going to give it a try next time out to see if I can’t gain a bit of power that way also .
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Valve spring is useless, none of my guns have it. Been like that for years.
Marko
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Works well for me. ;)
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I have a problem:
(https://live.staticflickr.com/65535/48512548981_4c4c0f8071_z.jpg) (https://flic.kr/p/2gUTuEi)388-dimple (https://flic.kr/p/2gUTuEi) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
That's tail of a .257388 that has been loaded in and pushed out, there's about 1.5mm deep dimple there caused by probe nose. The tail of the bullet is actually blocking part of the barrel port which would explain my speed issues with that bullet. So, it looks like I need move the chamber forward by 1.5mm. Now I do have those bullet shaped rubber adhesive grinding things, should I put one on a drill and size for a tight fit with sand paper and then slowly grind in to barrel until the probe no longer damages the bullet base?
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Guess I had that right, anyways.... *grin*…. If you had used a larger probe, you probably wouldn't have been able to load that bullet and would have known right away.... Too slender a probe can be a problem with "snug slugs".... Actually you were probably expanding the base of that bullet and making it a really tight fit in the chamber, too....
Bob
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Well now , thats not good . You can IMO do two things . One is to do as you’re suggesting and the other would be to buy the throat reamer from http://pacifictoolandgauge.com/6-off-throat-and-neck-reamers/958-17-cal-throating-reamer-hss.html (http://pacifictoolandgauge.com/6-off-throat-and-neck-reamers/958-17-cal-throating-reamer-hss.html)
There is another option which is to bring it to a local gunsmith and have him open it up .
I chose the pacific tool route as I had a few .257 barrels to fit . Saved me time and aggravation .
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Air usage from yesterday, started with 240 bar in a 12 litre dive bottle. Took about 70 shots in comp and after that I had 205 bar left in the bottle. I need to downtune a bit after I get the barrel sorted out, that's only about 150 shots from a fill at the diveshop. Although the bad weather at the range had something to do with it, the bottle showed 220 bar this morning after being inside over night.
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Although the bad weather at the range had something to do with it, the bottle showed 220 bar this morning after being inside over night.
There was like 16-17 C max. yesterday at range so your house is probably warmer than that. Don't make any adjusments on that gun because of air consumption. It looks to me you got that gun shooting better now than it was before. It is a risk of loosing that vs filling bottle often. And when you are coming on range Timo offers filling bottles so your bottle will be full vs dive shop filling.
Just my 0.2€
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A few degrees C will hardly make a noticeable difference in pressure in a tank.... it is relative to Absolute temperature (Kelvin)…. Raising the pressure from 16*C to 22*C (289*K to 295*K) will increase the pressure only 2%.... in your case about 4 bar.... Your tank temperature, immediately after shooting, may have been depressed because of expansion to some degree, of course....but it would take about 20*C to change the pressure from 205 bar to 220 bar....
Bob
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Riku, I guess you didn't notice our full service. I have been in every meeting we have ever had and I have had my compressor there too since I got it. For 5€ per happening you can have so many fillings you need and your bottle full when you leave if you want. So please next time just bring your bottle to line and leave with it more full you'll ever get it from scuba shop.
That 5€ i've set for covering maintenance costs only and we pay that once every time there for use of power anyway. Come with empty bottle, shoot what you want and leave with full, it is ok. Besides, we are not living that far from eachother but I am travelling a lot. Considering what is possible it is achiavable for you. Do not spoil what you have just for lack of air, there is no real lack of air.
Good I hate this laptop keyboard...
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There might be long winter, whirling wind, rain and dark and too short ranges and every kind of miserable things here but we are not in need of air. ;D
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Riku, I guess you didn't notice our full service. I have been in every meeting we have ever had and I have had my compressor there too since I got it. For 5€ per happening you can have so many fillings you need and your bottle full when you leave if you want. So please next time just bring your bottle to line and leave with it more full you'll ever get it from scuba shop.
That 5€ i've set for covering maintenance costs only and we pay that once every time there for use of power anyway. Come with empty bottle, shoot what you want and leave with full, it is ok. Besides, we are not living that far from eachother but I am travelling a lot. Considering what is possible it is achiavable for you. Do not spoil what you have just for lack of air, there is no real lack of air.
Good I hate this laptop keyboard...
Thanks Timo, I'm certainly taking your offer next time. I noticed that there was also a small dimple on tail of those 257420s cast from 2% tin mix but they still managed sub 1" groups. Same bullets cast from wheel weights did not get the dimple.
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Riku, when I originally sent you the barrel . I had cut the leade the same depth as what I had done to my conversion . I loaded a 257388 just to see if it was indeed punching a hole in the base . Yep big ol punch hole . So that makes two of us with the same problem . I don’t shoot that long of a bullet from that rifle anyhow . A Cothran powered discovery takes care of the long ones ,the only problem with that is I have to refill every second shot .
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After using up four of those rubbery adhesive bullet shaped grinding things and after making a new probe nose the 388s finally go in smoothly past the barrel port and there's only a very slight mark at the tail. I now get following shot string:
210 bar
912 fps
915 fps
918 fps
905 fps
162 bar
That's 161 fpe and I can go down to 170 bar pressure while still keeping adequate velocity. 420s were still zinging at 1000+ fps at 200+ bar, although I only got 3 shots from about 205-165 bar.
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Well done. That’s a nice string at that power for a relatively small volume of air . That betters what I’ve got power wise , but I remembered the barrel length was at close to 32” . Mine is now at 22”
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Riku,
It sure sounds like you need more hammer weight or more spring . Surely you’ll have it worked out . I shared a couple PM’s with Knifemaker and he told me he’s been running with no valve spring for some time . I’m going to give it a try next time out to see if I can’t gain a bit of power that way also .
seeing as to how I'll be employing a 70-35 in my hunting efforts, this intrigues me. How does this concept work? How about the dual hammer spring mod?
Excellent work, BTW. I'm quite new into the PCP world, so I can't even imagine how to do a conversion yet. Although if I get a Sumatra .25, I may look into converting it into a .357. ;D
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Riku,
It sure sounds like you need more hammer weight or more spring . Surely you’ll have it worked out . I shared a couple PM’s with Knifemaker and he told me he’s been running with no valve spring for some time . I’m going to give it a try next time out to see if I can’t gain a bit of power that way also .
seeing as to how I'll be employing a 70-35 in my hunting efforts, this intrigues me. How does this concept work? How about the dual hammer spring mod?
Excellent work, BTW. I'm quite new into the PCP world, so I can't even imagine how to do a conversion yet. Although if I get a Sumatra .25, I may look into converting it into a .357. ;D
If you want to tune your big bore Evanix/Winchester these threads should get you started:
https://www.gatewaytoairguns.org/GTA/index.php?topic=58699.msg561422#msg561422 (https://www.gatewaytoairguns.org/GTA/index.php?topic=58699.msg561422#msg561422)
https://www.gatewaytoairguns.org/GTA/index.php?topic=110075.msg1050388#msg1050388 (https://www.gatewaytoairguns.org/GTA/index.php?topic=110075.msg1050388#msg1050388)
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Riku,
It sure sounds like you need more hammer weight or more spring . Surely you’ll have it worked out . I shared a couple PM’s with Knifemaker and he told me he’s been running with no valve spring for some time . I’m going to give it a try next time out to see if I can’t gain a bit of power that way also .
seeing as to how I'll be employing a 70-35 in my hunting efforts, this intrigues me. How does this concept work? How about the dual hammer spring mod?
Excellent work, BTW. I'm quite new into the PCP world, so I can't even imagine how to do a conversion yet. Although if I get a Sumatra .25, I may look into converting it into a .357. ;D
If you want to tune your big bore Evanix/Winchester these threads should get you started:
https://www.gatewaytoairguns.org/GTA/index.php?topic=58699.msg561422#msg561422 (https://www.gatewaytoairguns.org/GTA/index.php?topic=58699.msg561422#msg561422)
https://www.gatewaytoairguns.org/GTA/index.php?topic=110075.msg1050388#msg1050388 (https://www.gatewaytoairguns.org/GTA/index.php?topic=110075.msg1050388#msg1050388)
Thanks, rkr! 8)
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Yep those are pretty much the tuning bible for the Evanix big bores . The twin spring set up works very well in this platform with some mods to the adjuster and the correct springs .
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rkr lost me about 2 pages in. :o
I don't have precision tools, and I have even less spare parts. Heck, I couldn't even rebuild a hand pump properly. :(
Looks like I'll have to send some business to Mr. Piatt. Oh well...gotta pay to play.
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Such a shame that Evanix (Mr. Lee) has opted to drop support for U.S. Evanix owners. No parts avaliable.
At least people like Ric. Jyself (to a limited extent) and Hobby are parts independent. LOL!
Fantastic platform that will die a slow death in the U.S. due to the lack of interest from the manufacturer in servicing our needs.
It feel terrible about suggesting Evanix to JSAR who went all in dealing with them, only to have the rug pulled out from under them as Evanix's first action with them. they delivered gun, sent a few replacement mag's and the disappeared from doing business with yet another U.S. company. GRRRRRR!!!!!
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I was fortunate enough to get some replacement parts from Mr. Lee again this week . Let me tell you he does charge an arm and a leg for both the parts and the shipping . He wasn’t able to get me all the parts as some were out of stock he told me .
It really is a shame but for future problems I also secured a local machine shop that will reproduce anything I can’t handle .
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Even if parts were available they are mostly made of recycled tincans or some similar material. Just think about snapped valve stems, sears that wear out to become dangerous and sidelevers that bend to banana shape. That's just steel parts, the aluminium alloy they use is really soft - scaringly so.
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I've written Mr. Lee three times now over the past year requesting a price on a few parts. I was courteous and respectful, and thanked him for the workmanship on the RS II.
Never so much a hint back. GRRRRR!!! :(
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Well heck. :( I was looking at some other Evanix offerings, but I guess I'll pass on that now.
Looks like I'll be getting that refurb Herc Bully in 45 for my big bore antics. Or maybe .357 depending on how this Winchester shoots.
Maybe a JSAR Hawk in .30 to fill the void of my soon-to-be-gone .25 Boss.
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I had rick Morrill bore out my jkhan .22(rainstorm) and Evanix.30 and put a solid stem for the valve on both. I’m sure I’m getting a tad blowby around the stem but it will still hit 120 ft lbs @3200 and 65 for the jkhan. I love the smith side levers. Everything else seems to be rock solid. Love to have a .25 or .257 rainstorm 😉, but may have to get something different someday.
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If the seller could ship to Canada , I would still buy the Windy City in the classifieds . It’s the older version with the “Hatsan “ style magazines and an aluminum cylinder . Even with parts problems , these rifles still put a smile on my face whenever I pull the trigger . I’m going to get one of the Kral hardened trigger sear from JSAR for the Winchester . Other than that the only parts needed should be orings .
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I wonder why in the world some refuse to ship to Canada. They do know that Canada has regular mail service. Yes? Odd!!!!
I spoke to the station master at the unit in Temple Texas, and he said there was no issue with Airgun anything. None. and that anyone saying different is ignorant of the Laws and Regulations.
Just flat strange!
I too use solid valve stems. to prevent blow by, simply put an o ring on the stem in the valve body. The pressure will force it against the wall on the high pressure side preventing blow by.
Knife
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Hmm...I think I need to start another thread on this. Hardened sears, solid stems, etc.
Perhaps there is hope.
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“I too use solid valve stems. to prevent blow by, simply put an o ring on the stem in the valve body. The pressure will force it against the wall on the high pressure side preventing blow by.”
Never thought of that Mike. Next time they are apart I’ll do that. Still haven’t radiused either valve or turned the stem. Love to pick up another 30-40 FPS for free😉
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I wonder why in the world some refuse to ship to Canada. They do know that Canada has regular mail service. Yes? Odd!!!!
I spoke to the station master at the unit in Temple Texas, and he said there was no issue with Airgun anything. None. and that anyone saying different is ignorant of the Laws and Regulations.
Just flat strange!
I too use solid valve stems. to prevent blow by, simply put an o ring on the stem in the valve body. The pressure will force it against the wall on the high pressure side preventing blow by.
Knife
Knife, how's your velocity spread with that o-ring on the stem inside the valve tunnel? I was considering that approach but I was worried it would slow down the valve closing if the o-ring binds on the stem. My Blizzard has little to no blow by with solid stem but my Sniper X2 blows air out of the hammer guide slot.
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I use Knife’ o ring on stem method and have not had any velocity swings that I would blame on it . I use it on my Hatsan also .
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None at all Ric. But I do mirror polish the valve stem, and lightly lube the stem with silicone 100 wt oil. the o ring is almost a loose fit. It is a polly cast o ring. Under a lot of pressure it expands slightly and locks down on the opening. However, when you shoot, the pressure drops so it will allow free movement of the stem to close. ;)
If the o ring is too tight, I hone the inside dia. until it is a light slip fit.
I love a light slip fit! ;D
Mike
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A project is never over it seems. While the gun did well in competitions it was wiggly on the bench rest causing flyers and spread groups. So, I decided to make a new stock for the gun. I bought some alder planks and glued them together to make this BR stock. 100mm wide at the front it wont tilt anywhere when rested. As a new thing I screwed on a piece of thread bar to the barrel band that gives me a second attachment point for the action right at the front which should stiffen up the action for less flex.
(https://live.staticflickr.com/65535/49983319068_d00d8aabf4_c.jpg) (https://flic.kr/p/2j9Rznf)evanix-br-1 (https://flic.kr/p/2j9Rznf) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
(https://live.staticflickr.com/65535/49984095827_f7d921742f_b.jpg) (https://flic.kr/p/2j9VygD)evanix-br-3 (https://flic.kr/p/2j9VygD) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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Very nice job.. that’s a great looking stock and nice grain. Been following this thread as I would love to have a 257 traditional stocked rifle myself. Great thread!
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Very nice job.. that’s a great looking stock and nice grain. Been following this thread as I would love to have a 257 traditional stocked rifle myself. Great thread!
Thank you. Now I need a new front rest bag with wider slot, any good ideas what to use in place of that stock bag? I know there's a wider bag available but I need to DIY something for the next weekend.
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It was time for after season check for the gun. The gun did well past season scoring some first places in BR and it worked very well even in our silhouette shooting serie. For silhouette I need at least 150 fpe at the muzzle and more is better so it's different tunes for BR and silhouette. I took the gun apart and found nicked barrel/probe o-ring, split o-ring in the valve block and the depinger was in really poor shape.
(https://live.staticflickr.com/4109/35732916106_c714c9f104_c.jpg) (https://flic.kr/p/WrAx3s)depinger-mk2_zps0ba86aa8 (https://flic.kr/p/WrAx3s) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
The depinger had four 6mm holes in that disc and it was held in place with a M4 nut in a thread bar. The nut had stripped it's threads and the disc was at the valve block. I made a new disc with four 8mm holes and used three nuts in the thread bar.
The gun had emptied itself and I suspected the valve seat which was damaged earlier. I made a new conical seat which allowed me to reduce the poppet diameter by 0.5mm. That doesn't sound much but it's 11% reduction in force keeping the valve shut.
I then started wondering about the tune of the gun. While it made decent power it was an air hog and it was clearly pushing air out of the barrel long after the bullet was gone. So I decided to see what would happen if I lightened up the hammer a bit.
The original hammer had extra weight "tophat" inside and the whole thing weighed 56 grams. Removing the tophat dropped the weight to 38 grams, a nice one third reduction. Following table shows what happened when I dropped the weight while keeping the same dual spring setup and tension then how it went when I swapped in a 2mm wire spring.
HeavyHammer max LightHammer max LightHammer SSS
bar/shot 14,5 10 8
max vel m/s 297 291 302
max vel fps 974,16 954,48 ´ 990,56
vel peak pressure 200 190 200
energy 151,6907243 145,6237145 156,841148
I was able to cut the air usage almost in half which also reduces the recoil quite a bit. The downside is that the trigger is heavier with the SSS setup. An alternative would be to use the old dual spring and just live with the recoil and air usage. The heavy hammer setup can also be downtuned to 920 fps which I like for BR by turning the adjuster out 4 turns, that also gives me 8 bar / shot ... I guess I need to play with this a bit more. Some stock modifications next.
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Nice tune Riku. I really need to take mine off the rack and shoot it. Seems like once I find a good tune and I’m happy with where it shoots . I’ll hang it up and move onto another rifle. There is a local farmer that needs to reduce the coyote population. I really should go visit him . I think I have the solution ........
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Excellent results. See a similar trend where a Light hammer operating with the same spring energy driving it can SPEED UP the opening cycle and increase amplitude of the air driving out the projectile. And being light can stop faster at max lift reversing direction faster chopping dwell w/o effecting power.
In the case shown actually gain a bit of power due to the higher amplitude of the pressure pulse happening before projectile gets going.
Good stuff !!
Scott S
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This gun has 31" barrel, if it was shorter I think I would have seen increase in speed with lighter hammer. I also think that around 980-990 fps is the practical velocity limit for 72 grain bullets at 200 bar with this barrel length. I was able to hit 1030 fps when I overfilled to 210 bar so there's more to be had with higher pressure.
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Awesome build. Your results with the lighter hammer are in line with what I have seen in various guns.
After following Scott's lead with light/ultralight hammers I have a simple approach to hammer strike. Configure it as such you can build your desired energy levels with as fast moving of a hammer as you can comfortably cock. Of course this is all part of a system which includes other variables such as valve throat and pressure, buy generally speaking I like very light, fast moving hammers.
Cocking with one finger is of no value to me if it is accomplished with a heavier, slower moving hammer.
BTW, I saw similar numbers with a 27" barreled Bulldog .257 conversion. It maxed out a little over 165fpe on 3000psi. Bear in mind this powerplant does just over 300fpe in .357, porting is in the .300 range. Have a 35" 25-20 blank in process, I hope to see similar numbers just without running so hard.
I really like your depinger setup, thank you for sharing.
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Thanks Mike! I've played a bit more and increased the strike length some 3mm. The power was down a bit as the hammer got lighter but swapping the main spring from 1.5mm wire to 1.6mm brought the velocity back to 990 fps. The problem with heavy springs is not the cocking effort (sidelever is easy to cock anyway) but the trigger gets heavier as there's more force pushing against the sear. As this is a BR gun a good trigger is one of the must haves. I'm actually not sure whether the current trigger pull is too heavy or not. The problem is that I need two tunes for this gun, one that slings those 257420s at 980+ fps for silhouette and another for BR where about 920 fps is enough (seems to be sweetspot for accuracy). I could use different springs and hammer for that but the threads on the block are already worn out so I'd like to switch tunes by RVA only.
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Thanks Mike! I've played a bit more and increased the strike length some 3mm. The power was down a bit as the hammer got lighter but swapping the main spring from 1.5mm wire to 1.6mm brought the velocity back to 990 fps. The problem with heavy springs is not the cocking effort (sidelever is easy to cock anyway) but the trigger gets heavier as there's more force pushing against the sear. As this is a BR gun a good trigger is one of the must haves. I'm actually not sure whether the current trigger pull is too heavy or not. The problem is that I need two tunes for this gun, one that slings those 257420s at 980+ fps for silhouette and another for BR where about 920 fps is enough (seems to be sweetspot for accuracy). I could use different springs and hammer for that but the threads on the block are already worn out so I'd like to switch tunes by RVA only.
I re-read this thread and realized I was somewhat blending your and Denis' build in one. Now I have a better understanding of the 2 builds....
That silhouette stock is sweet, I bet that really allowed you to focus on other areas during the shot, just keeping the gun vertical is no longer a major effort I'm sure.
I know this would create a whole development project in itself, but I have seen balanced valves that behave very much like what you are asking for. Big porting, unregulated. Simply adjust the RVA to go up/down across say a 100fps range, while having good ES throughout that range of adjustment. The valve Bob described in his final version of the simplified balanced valve can very much perform this manner. I don't know if you recall when the original SS valves came out they delivered regulated-like strings in unregulated format.
If you wanted to take it to the next level, this very well may be it----potentially with the added benefit of reducing hammer spring requirements having a positive impact on trigger pull.
But I could also see the point of view where you have a good thing going with a proven, stable gun. I would almost be scared to touch it, lol...
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Thanks Mike! I've played a bit more and increased the strike length some 3mm. The power was down a bit as the hammer got lighter but swapping the main spring from 1.5mm wire to 1.6mm brought the velocity back to 990 fps. The problem with heavy springs is not the cocking effort (sidelever is easy to cock anyway) but the trigger gets heavier as there's more force pushing against the sear. As this is a BR gun a good trigger is one of the must haves. I'm actually not sure whether the current trigger pull is too heavy or not. The problem is that I need two tunes for this gun, one that slings those 257420s at 980+ fps for silhouette and another for BR where about 920 fps is enough (seems to be sweetspot for accuracy). I could use different springs and hammer for that but the threads on the block are already worn out so I'd like to switch tunes by RVA only.
I re-read this thread and realized I was somewhat blending your and Denis' build in one. Now I have a better understanding of the 2 builds....
That silhouette stock is sweet, I bet that really allowed you to focus on other areas during the shot, just keeping the gun vertical is no longer a major effort I'm sure.
I know this would create a whole development project in itself, but I have seen balanced valves that behave very much like what you are asking for. Big porting, unregulated. Simply adjust the RVA to go up/down across say a 100fps range, while having good ES throughout that range of adjustment. The valve Bob described in his final version of the simplified balanced valve can very much perform this manner. I don't know if you recall when the original SS valves came out they delivered regulated-like strings in unregulated format.
If you wanted to take it to the next level, this very well may be it----potentially with the added benefit of reducing hammer spring requirements having a positive impact on trigger pull.
But I could also see the point of view where you have a good thing going with a proven, stable gun. I would almost be scared to touch it, lol...
I've been testing a balanced valve in my .45 Evanix and while it gave me nice reduction in opening force I could never make it seal properly. It always started a slow leak after few shots, from the "plunger" o-ring I would say. I eventually got frustrated and put together a normal valve that sealed immediately.
Now I have considered a balanced valve for this .257 as well but I came to a conclusion that it would not be good in this application. For BR I want as small fps variation as possible and with balanced valve the forces acting on the valve are reduced while friction is increased, thus the variations in friction come more pronounced and may decrease shot to shot consistency.
The stock is nice but I will add a but hook to it for standing position shooting. I have removable weight for it that I add for BR and remove for silhouette. I'm also considering whether a rear monopod would be useful, anyone tried one of those things for BR?
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One more tune, a bit lightened up hammer with longer stroke and 1.6mm wire stiff 12mm diameter spring = 299m/s or 980fps. That same spring + 15mm spring around it made 10 fps more while having stiffer trigger. I'm actually out of bullets so that's it for now. Action is now bedded to stock so time to figure out the hook and buttplate.
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It's been 3 years since I started this conversion and the gun is now producing pretty good results. The latest mod was a thimble for the transfer port which allows me to index the barrel. These 100M groups I shot today tell me it was a good modification (measurements ctc):
(https://live.staticflickr.com/65535/51489255528_880bff418a_k.jpg) (https://flic.kr/p/2mrVTNY)20210918_153330 (https://flic.kr/p/2mrVTNY) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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Good shooting! 5 shot groups probably? There is one competition left although we shoot 13 shots and 10 best counts. But you probably noticed that on Sihry's page. That gun gonna be hard to beat at 5x5 Bech rest competition's if everything goes well... But that range what we use has own tricks to spoil groups but you already knowing that. ;D wind is tricky there.
Are you taking part on that last competition?
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Good shooting! 5 shot groups probably? There is one competition left although we shoot 13 shots and 10 best counts. But you probably noticed that on Sihry's page. That gun gonna be hard to beat at 5x5 Bech rest competition's if everything goes well... But that range what we use has own tricks to spoil groups but you already knowing that. ;D wind is tricky there.
Are you taking part on that last competition?
Yes, 5 shot groups at Iittala range, it was relatively calm there. The groups were actually better than what I shot with my Anschutz 54 and SK Standards. Those shown were the best groups, there were strange flyers occasionally so the gun is not all spot on yet - average groups size around an inch I'd say. My guess is that thimble and barrel are not 100% lined up which causes occasional slight damage to bullets when loading. I'll try to get to the last competition, I hope life doesn't get in the way.
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The thimble and the barrel were indeed misaligned, there were small lead shavings at the junction point. I made a new thimble version, I hope this will be the final one - bullets show no damage when loaded and pushed back.
(https://live.staticflickr.com/65535/51495710438_519f11d8b1_k.jpg)
(https://live.staticflickr.com/65535/51495711803_12390fecfb_k.jpg)
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And now just give me that address where to send last competition's first price ? :P
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And now just give me that address where to send last competition's first price ? :P
You should have my address Teemu, but let's do the actual competition first - we are also shooting from standing position and that's not my forte ;D
One more mod, a longer trigger blade. Shaves off few ounces from the trigger pull which is quite horrible when compared to Anschutz match trigger:
(https://live.staticflickr.com/65535/51502942784_33cc7c8b2c_k.jpg)
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When you start tinkering it's hard to stop, a muzzle brake to reduce the gun movement on bench rests:
(https://live.staticflickr.com/65535/51510395982_854de4425b_h.jpg)
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Putting that lathe to good use!
Have any regrets, other than the fact why didn't you buy it sooner?
Marko
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Putting that lathe to good use!
Have any regrets, other than the fact why didn't you buy it sooner?
Marko
You just put my thoughts to words, I should have bought a lathe years ago. I'm just at the beginning of the learning curve but making small parts is fun and a good way of learning things.
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Great work Riku. I seldom shoot my converted .257 as I don’t shoot paper much these days but have been focusing on hunting. I’ll return to it one day and hope to make better power for heavier and better BC bullets. The most accurate I have right now is the 257338 bullet . I just need to push it faster and the way my rifle is set up right now , I’m tapped out at about 720fps. I’m gonna blame it on flow as I don’t have any other excuses.
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Great work Riku. I seldom shoot my converted .257 as I don’t shoot paper much these days but have been focusing on hunting. I’ll return to it one day and hope to make better power for heavier and better BC bullets. The most accurate I have right now is the 257338 bullet . I just need to push it faster and the way my rifle is set up right now , I’m tapped out at about 720fps. I’m gonna blame it on flow as I don’t have any other excuses.
Thanks Denis! That is rather low with 257388s, I was shooting them at 920 fps. You need barrel size porting and 30" barrel for that though. Oh and lot's of dwell as well.
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Some succesful tuning finished. I've had problems with stiff trigger and it has caused me occasionally pull shots. While the longer trigger blade helped a bit it didn't solve the problem. I then considered swapping the trigger parts to new model Kral trigger parts with a drop down sear but I was unable to get them as spares anywhere. Making new trigger parts from scratch is a time consuming task so I thought I'd try the next best thing, reducing the hammer spring force while keeping the power I have. I can see you thinking "this is just another balanced valve build" but no, I took a different approach. Thank's to Mike's experiments/builds with small diameter valve stems, I decided to see what can be gained by reducing the forces that close the valve.
So, I got some 2mm HSS rod, piece of brass rod and some peek and it was time to put my lathe to work. I took an extra valve housing I had (Thanks Timo) which has 7.5mm valve tunnel and drilled out and threaded the stem tunnel. Then made a threaded brass insert for 2mm stem and screwed that in place. The valve itself is as low tech as can be, 2mm stem and a peek poppet that's slightly streamlined (no valve spring) to reduce airflow effect on poppet.
(https://live.staticflickr.com/65535/51598741156_a3372809c9_k.jpg)
(https://live.staticflickr.com/65535/51599638125_2cc1dd6071_k.jpg)
I put the gun together and started tuning. Results really made no sense, first I had a speed jump up by 16 m/s (53 fps) and I though I have something here. The speed then kept dropping what ever spring/hammer weight combo I tried. I took the gun apart and found that the stem which earlier came out 6.5mm from the housing was only out 4mm now... Looks like it was slowly penetrating the peek poppet. After some thinking I decided to add a grub screw at the rear of the poppet to stop the stem from moving.
(https://live.staticflickr.com/65535/51599638225_eb032c75c0_k.jpg)
Time to test again, this time the stem will stay 6.5mm out, I don't really see that 5mm grub screw stripping threads. I started with the lightest spring I had, 1.5mm wire 12mm diameter stainless steel spring and a bronze tophat for extra weight at the hammer. 205 bar and I got 305 m/s, that's 1000 fps and 160 fpe. That's more than I had with extra heavy springs and 4mm stem valve in a 8mm valve tunnel. I have a winner here. Taking out the hammer weight dropped the speed down to 262 m/s so that was a no go. 160 fpe is really enough so no need to try heavier springs. Trigger is much better now with greatly reduced hammer spring force pushing against it. A succesful tune and I'm happy. Next thing is to test how the stem works in a long term use, I guess I need to cast more bullets as I have only 20 left from my last casting session.
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Smaller stem pays two benefits, less closing force, and increased flow through the throat area.... Looks like you nailed it!....
Bob
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Smaller stem pays two benefits, less closing force, and increased flow through the throat area.... Looks like you nailed it!....
Bob
Yes and it was all about the stem diameter and less closing force giving me same dwell with less hammer strike. The old setup had a 2.5mm stem (narrowed in the middle, 4mm at the end) in a 8mm valve tunnel so it could actually flow more than this 2mm stem in a 7.5mm tunnel. The big stem valve in the photo is stock Evanix valve.
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Some extra tinkering for the new valve housing to make it more user friendly, a depinger to rid that horrible twang and a valve lift limiter to prevent that poppet from coming out and entering in to the airtube.
(https://live.staticflickr.com/65535/51624268147_03b875e280_k.jpg) (https://flic.kr/p/2mDRSmK)2021-10-24_05-14-33 (https://flic.kr/p/2mDRSmK) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
(https://live.staticflickr.com/65535/51625747449_ccd262748b_k.jpg) (https://flic.kr/p/2mDZs6X)2021-10-24_05-15-24 (https://flic.kr/p/2mDZs6X) by abbababbaccc (https://www.flickr.com/photos/11843711@N08/), on Flickr
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A bit of random testing, 200 bar and normal bullets shoot at 300 m/s, bullets with blue PC shoot at 304 m/s -> 12 fps difference.
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A bit of random testing, 200 bar and normal bullets shoot at 300 m/s, bullets with blue PC shoot at 304 m/s -> 12 fps difference.
What lube and same sizing die used?
Marko
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A bit of random testing, 200 bar and normal bullets shoot at 300 m/s, bullets with blue PC shoot at 304 m/s -> 12 fps difference.
What lube and same sizing die used?
Marko
Both unlubed, both sized with the same die. Now that you mentioned it I sprayed some bullets (both PC and non-PC) with CRC silicone spray and the result is still the same.
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Another small test with silhouette settings and powder coated bullets (all those I had left):
210 bar
310 m/s = 1017 fps = 165 fpe
308 m/s = 1010 fps
310
309
309
310
309
310
310
309
Decent spread and some 5 fpe extra power. I think that's all I can get from this gun with reasonable effort.
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Pressure / speed notes after slight down tune for the next range session:
210 bar = 307 m/s = 1013 fps
200 bar = 302 m/s = 990 fps
190 bar = 295 m/s = 967 fps
180 bar = 287 m/s = 941 fps
170 bar = 281 m/s = 921 fps
160 bar = 275 m/s = 902 fps
The gun is actually using 10 bar / shot so it's not too bad for this power level. I could tune it for less but I rather keep the potential to go past 1000 fps if needed.
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The FPE is pretty much proportional to the pressure, as it should be.... Nice job!....
Bob
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The FPE is pretty much proportional to the pressure, as it should be.... Nice job!....
Bob
Thanks! It's been a long project and a good learning experience.
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Good Work Riku. I haven’t chimed in for a while on this one but have been following. I don’t even remember where I left off with my Winchester as hasnt been shot in quite a while. You have given me a few ideas though for my next go at it. I’m thinking one full mag per fill shooting the 257420. Thanks for the ideas