GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Rdsail on May 11, 2015, 08:00:22 PM
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I got the parts from WAR. Bottle, Bottle adaptor and new Air tube.
My current build is a high power .25. I'm aiming for 100+ fpe.
I did had to bore out the brass fitting that connects the bottle to the bottle adaptor. It came with an opening of about ⅛ or 1/16. I did not measure it. I bore it out to .565 to match my valve throat which happens to be a WAR valve. For most people the plenum on the bottle kitshould be enough (50cc) for 50-65 fpe.
I had to modify the airtube to take .306 transfer port.
I'm still waiting for my breech and barrel to test out everything. Which is a TJ .25 26" barrel with threading and LDC. I will be putting Carbon fiber sleeve. The lead is for bullets and not pellet. I have a good assortment of casts and swags to test. All ranging from 40-65 grains.
Tube, block, bottle and 1.5 in guage.
(https://farm9.staticflickr.com/8863/17482090166_b68ccfbd1e.jpg)
I inlet the stock
(https://farm6.staticflickr.com/5459/17522597052_69a4f41e9d.jpg)
The set up is holding air. No apparent leaks so far.
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How long is the air tube?
cheers,
Douglas
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Did you have a custom breech made, or did you just order one from Crosman? This is something I'd like to do one of these days!!
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How long is the air tube?
cheers,
Douglas
My tube is 11 ¾ long
The breech is a .25 mrod breech
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What kind of shot count are you trying to get out of it at 100fpe?
Joe
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to tell you the truth. I have no idea. lol
My guess is that I could get 8-10 shots. This is uncharted waters for me
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My .25 Mrod with as received WAR valve 25 inch bbl and stock P tube gives me ~ 8 shots @ 94 FPE max and 91 avg at 3400 fill with 53 gr slugs. I see no reason you wouldn't get at least the same or better with a heavier slug and the I assume 13 (213cc) inch tank if you dare fill to 3400. ;)
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cool. Then I should be able to get more shots. I just don't have any Idea. My porting is fairly large so it should be able to handing a lower fill pressure or so I hope.
I also will have 7in more of barrel. That will help a ton
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My bbl is 25" TJ w/ stock shroud. After all said and done a 28" would have been better fitment wise. Maybe next time. :D
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very cool! Mine is longer than yours. But no shroud for me. ;D
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That's me, always the short one. 8)
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I have a 28" TJ barrel on the bench, lets see what this can do!
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I really like the bottle idea. I have a synthetic stock too. How did you go about cutting the stock? I am a little concerned about it. Hole saw ?
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BTW, shameless plug for Shorty^^^^ - try his 2.14" dual hammer spring if he is still making them. Really.
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yes I used a hole saw and a round sander.
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Looking good Dan.
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I would consider slightly shorter barrels. The next one I am doing is 25" and .590 OD....but .30 pellet, not .25
cheers,
Douglas
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With the Mrod breech are you going to use magazine or SS tray? I ask because I can't get 65 Gr to fit in mag.
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50ish gr. is about the longest for the mag....
Bob
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For those 75 grain + slugs
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I'm curious what's the diameter on your bottle? How much gap between the bottom of the shroud and bottle?
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I'm curious what's the diameter on your bottle? How much gap between the bottom of the shroud and bottle?
Bottles should be 2.375 and not stick up past the top of the air tube, so as much clearance as the OE has between the shroud and air tube.
cheers,
Douglas
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Douglas you think a 2.400 bottle would be ok?
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My TJ .25 barrel finally came in. I still need to put the CF sleeve but tomorrow will be the big day. Power test!
(https://farm8.staticflickr.com/7786/18363580115_0302b4bb38_b.jpg)
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Looks good to me...:)
Do you know if the 25's can be had in larger-than-1/2" OD? I am having some issue resisting the temptation to bore the barrel port to .5625 and run the barrel one size up. That is the plan for the B-Rod 30 cal anyway; that barrel starts at .590...skim it and see if it likes being bigger v. the 1/2 barrels.
cheers,
Douglas
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Right on!!! Let it rain.
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I don't know if there are he has bigger OD barrels.
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You can get the .25 cal TJ's liners in 7/16", 1/2", or 9/16" OD.... The largest .30 cal is 0.590", and the largest .357 is 5/8"....
Bob
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Can't wait to see the numbers Dan. Looking good.
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First update: All shots made teathered at 2600psi
My first try I got 85fpe with 50g bullets but some issues came up. The first is that my tport is not sealing well. this is 50g going at 880fps The second issue was that I'm getting tons of hammer bounce. I went back and try to fix both things. I removed the extra weight on the hammer and made a stainless steel tport.
The second test. I got 94fpe with 50g bullets. I still have hammer bounce but very little in comparison and the Tport still leaks some air. The gun is very loud even with the 10" 1.5 dia LDC.
I should get more power if I up the fill pressure and I need to fix the tport. it will interesting to see when I try other bullets but I'm saving them for when I do the accuracy testing.
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Following!!
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94fpe your almost there.
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Most likely one of 2 is going on:
-The air in front of the hammer is getting trapped.
-Too much air is escaping through the stem. I bet this is it.
Edit: I guess it could be TB blow by as well, which you are seeing.
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rjorge = Are you talking about the hammer bounce?
If you are, then no, hammer bounce is caused by the velocity of the return of the hammer compressing the spring and is pushed fwd again with enough force to knock open the valve again (repeatedly)
The way to fix it is what Daniel is already doing. Making the hammer lighter, reducing the pre-tension of the hammer spring(or making the spring super hard, but then hard to cock) increasing throw, or a combination of these to allow minimal bounce.
The right way of course is to have some sort of (slingshot) mechanism to take out the chance of the hammer re-compress the hammer spring on it's return. But this cost more and is more complex.
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This is definitely air from the tport. It is coming from the sides of the breech. It's not that much which is good.
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I had that happening Daniel, I made a tport in brass, then chamfered the top, and made the same angle inverted recess on the receiving end (barrel or thimble) I.e. not a stepped one. Only using an O ring on the valve end of the t-port.
I am not sure how well that would work in your application (mine is the .22 - at 40+fpe)
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Tomg, yes I was talking about hammer bounce. If you haven't experienced any of those issues, they will most definitely cause excessive hammer bounce. A lighter hammer is only a band aid to the issue. I have experience both as well as many others here.
The blow by air causing the spring to compress even further after hitting the valve...
Btw, a hammer spring that "rattles" at 0 preload, slightly shorter, is the best cure for hammer bounce, outside of a mechanical brake.
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rjorge- I must apologize, I've never heard that those could cause hammer bounce.
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I know this may sound crazy and possibly not work but, I'll throw it out there anyway ( just food for thought). On my .357 marauder build I find it difficult get larger than .18" on the transfer sleeve without a good seal due to the transfer port at the oring locations being so thin. It either bends from the pressure or assembly bends it.
So I have been kicking around the idea to eliminate the transfer sleeve completely by using an entire upper receiver to air tube gasket. Possibly a thin sheet of high pressure gasket material mated and punched to the dimensions of the both.
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shorty,
I made my opening .303 instead of the .25 original. I have plenty of wall. I'm going to use PTFE tubbing and compress it some so it seals.
here is a picture with the CF tube over the barrel and LDC installed.
(https://farm8.staticflickr.com/7761/18396659381_79dc4414f9_b.jpg)
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Sounds good and looks good. Everyone needs a name. What are ya gonna call it?
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shorty,
I made my opening .303 instead of the .25 original. I have plenty of wall. I'm going to use PTFE tubbing and compress it some so it seals.
here is a picture with the CF tube over the barrel and LDC installed.
(https://farm8.staticflickr.com/7761/18396659381_79dc4414f9_b.jpg)
I made my TP out of Acetal, it doesn't leak.I made a couple extras too. Hand fitted, by parting it a little long, chuck it up and hit it with 180 grit to length. The Acetal has enough "give" to seal when fitted a little long.
Have you got any or will you have any before and after groups with the CF tube?
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I have not shot groups with out. I'm waiting for the epoxy to cure well and better weather to give it a full test. I might have to go somewhere else other than my house to shoot it. It is a bit loud at 94fpe.
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Beautiful work Rdsail ;),
I can't imagine what she'd sound like w/o the LDC? That thing is huge :D.
Kirk
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Quick Update:
got it to shot 103 fpe at around 3000psi but it uses 150psi per shot. it is an airhog. lol
I think will tune down to about 80 fpe to up the shot count. I'm still impresses with it. I think it is wasting lots of air due to hammer bounce. you can hear it. The there is very little bounce once I reduce power.
I did my testing in the basement and had many error readings. Once the rain stops I'll test outside for more accurate readings.
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Pretty typical.... Do a velocity vs. preload curve and it will be obvious where to tune it.... Here is what my Grizzly did at two different pressures....
(http://i378.photobucket.com/albums/oo221/rsterne/Flying%20Dragon%20PCP/Grizzly%20Hammer%20Preload_zpsgcucivpj.jpg) (http://s378.photobucket.com/user/rsterne/media/Flying%20Dragon%20PCP/Grizzly%20Hammer%20Preload_zpsgcucivpj.jpg.html)
When you are up on the plateau part of the curve, the gun is an air hog.... You have to dial it back to the knee, your tune will be somewhere about there.... One way to use those curves in an unregulated PCP, is where the two pressure curves cross, for a given pellet, is where you might find a tune using those two endpoints.... For example, using the red lines (45 gr. JSB), they cross at 2.7 turns out at 930 fps.... With the preload set there, you would get a shot string that starts at 930 at 2900 psi, climb to a peak, and then drops back to 930 at 1800 psi....
Bob
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Bob, My plan is to get some solid numbers as soon as it stops raining.
On another note, Travis (oldpro) made a recommendation of adding holes to the front of the hammer all the way to the back into where the spring goes in. I drilled 4 .125 holes and he also mention reducing the hammer spring length to be just shy of touching the hammer when it is in contact with the stem.
I did both things and the hammer bounce is gone. My air consumption went from 150 psi to about 50-75 psi. I did not measure it carefully. This is very impressive. I don't have power numbers but this simple mod made a huge difference.
Going back to rjorge, he was right! it is amazing how much air gets compressed by the hammer. you can feel a the air coming out of the back of the gun where you adjust the hammer spring. I made sure that the breech was not leaking air.
Thank to Travis for the suggestion!!!!
Edit: It forgot to mention that It is quieter!!!
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Hey Bob & Rdsail,
Great tuning basics to always be thinking about -> Thanks :D
Kirk
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Sounds like its starting to really come together! Good deal, and Please send that rain to SoCal we really need it.
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Bob, My plan is to get some solid numbers as soon as it stops raining.
On another note, Travis (oldpro) made a recommendation of adding holes to the front of the hammer all the way to the back into where the spring goes in. I drilled 4 .125 holes and he also mention reducing the hammer spring length to be just shy of touching the hammer when it is in contact with the stem.
I did both things and the hammer bounce is gone. My air consumption went from 150 psi to about 50-75 psi. I did not measure it carefully. This is very impressive. I don't have power numbers but this simple mod made a huge difference.
Going back to rjorge, he was right! it is amazing how much air gets compressed by the hammer. you can feel a the air coming out of the back of the gun where you adjust the hammer spring. I made sure that the breech was not leaking air.
Thank to Travis for the suggestion!!!!
Edit: I forgot to mention that It is quieter!!!
So after reducing the hammer spring length, what fps/fpe numbers are you getting?
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I will post numbers once the weather gets better. It is not raining today but to cloudy and dark to get good readings. The muzzle puts out so much air that if the lighting is not right I get lots of errors. Waiting is a pain.
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How did you drill the holes in the hammer? That thing is hard... I assume the .125 holes are axial, and right around the head of the striker?
cheers,
Douglas
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Update:
I found that air was leaking though the stem. I added an oring on the back of the valve that compresses with a thin alum plate and two screws. This fixed the leak. Now I'm shotting 49g cast bullets at 990fps which amounts to 107 fpe. I have a few of bobs BBTs that I believe are 51 or 51 grains. I wish I had heavier casts to try. The 55g swags I have just don't fit right in the barrel and it loose power. Does anyone have anything I can try out that is on the 55 to 65g range.
Just loving the results.
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Update:
I found that air was leaking though the stem. I added an oring on the back of the valve that compresses with a thin alum plate and two screws. This fixed the leak. Now I'm shotting 49g cast bullets at 990fps which amounts to 107 fpe. I have a few of bobs BBTs that I believe are 51 or 51 grains. I wish I had heavier casts to try. The 55g swags I have just don't fit right in the barrel and it loose power. Does anyone have anything I can try out that is on the 55 to 65g range.
Just loving the results.
We're loving the results too!!
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I have some numbers for you guy. I'm using hunter supplies 49g .25s.
I reduced the power top around 80 fpe and shot a full string. I'm only have 1 turn on the preload. It maxes out at 990fps if I add the full preload.
Accuracy is very good but I have an issue. I'm having some side to side wiping. The pellets start in two locations from 30 yards. I have very little vertical stringing just two POIs about 6 in apart which is odd. I think I'm going to make a barrel band to lock the barrel to the bottle. I'll have this 3D printed so there is a perfect fit.
The only other problem I found is that my fill nipple shut valve will come out if I dont face the nipple down. I can put a spring behind it but that will block flow. Do you guys have any suggesting?
here are the number.
Click to view larger
(https://farm1.staticflickr.com/520/18413577608_f59972cbc2_o.jpg)
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Looks like about 21 shots within 4% if you start at 3000 and stop at 2200....
Bob
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that is about right. I need to order more casts from hunter supply. to test at higher power. I did some quick 5 shot strings and it gets flatter as the power goes up. I think when I'm all set and done will end up with around 90 fpe. Which will be 900-920 fps. I'm very impressed that I have a range of 33pfe with one spring. I still have a small leak off the tport which blow back through the hammer. I talked to lloyd and he offered to make me a delrin tport which I hope will fix the problem. I bet I can gain a bit of efficiency if I fix that.
Next week I'm going for vacation for almost two weeks so I'll have some time to get it sorted out once I get back.
Bob,
Your BBTs 50g that you sent me shot the best. I think at some point I'll have to order a mold and start casting.
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here is the barrel band ready to be printed. it uses 2 4-40 screws to tighten it.
(https://farm1.staticflickr.com/267/17984897764_e7f89d34b3_q.jpg)
(https://farm9.staticflickr.com/8854/18581166486_96873e8dc4_m.jpg)
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Very nice. I might have to hit you up for some printed parts...hmmm... ::)
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I did some more shooting yesterday and found that the bullets were clipping the end of the LDC. they where actually barely touching. I think I need to order the band asap to stabilize the barrel. I check the bore alignment and it is dead on.
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I'm getting better at drawing with Autodesk fusion 360!
Once I get it all I have to do is thread for the 4-40 screws.
(https://farm1.staticflickr.com/515/18082177634_9e41c5c6bb.jpg)
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I got the barrel band back. Here is a picture after smoothing and spray painted enamel flat back. it fits perfect
(https://farm1.staticflickr.com/383/19122521688_5e92611119_b.jpg)
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Nice, what material did they print it in?
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it ended up being Nylon-11
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Finally got to get the whole setup. I shot from 50 yards. So fart the only casts that shot well are Bob's BBT 51s. This was a quick test because I only had 18 bullets. This meant that in 18 shots I had to get the speed to around 880 and somewhat zero the gun.
I was tethered to my scuba tank at 2450 psi. I took a total of 14 shots. Once I to the power were I wanted ( It took 5 shots) I was shooting 880 with a spread of 8fps. But most shots where 1 to 2 fpe from 880. Also at the same time I was adjusting the zero.
51g at 880 is 87.7fpe 2.5 turns of preload
I do have to say I have to get used to the recoil and action movement.
(https://farm1.staticflickr.com/387/19633431835_1344fdb6d8.jpg)
First shot was the bottom lonely one. I adjusted elevation 2 time. the higher groups where the first adjustment and the middle group was the final adjustment. This was a total of 9 shots. The middle set is about ½ in. I did not measure it.
I'm very happy with the outcome.
now some other pictures.
(https://farm4.staticflickr.com/3737/19445401958_c961a904df_b.jpg)
(https://farm1.staticflickr.com/402/19012487283_d6a4b6a2c3_b.jpg)
(https://farm4.staticflickr.com/3724/19626389342_7bfdcffd5e_b.jpg)
This is what I was shooting and 2 shots will rip through it.
(https://farm1.staticflickr.com/424/19607250206_123dcc979e.jpg)
The hole to the left is 3 shots. The big hole is the 9 shots.
(https://farm1.staticflickr.com/300/19633429045_97a41cce1c_b.jpg)
Hopefully soon I will have 60g BBTs and I will be testing them. The sad part is that i'm out of BBTs so no more shooting for a while. I do have to thank bob for sending me a sampling of them a while back!
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looking good
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Looks good Daniel!!!
So that's the CF 1/2" barrel (now 0.625" od) ?
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correct
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Update:
Today I receive samples from Tom Buchanan of Bob's BBT's in .25 and 58.4g. He sent me two sizes .251 and .250 to test out. I can't wait to test them on my Mrod. I'm looking to shot them around 840fps which will give me 91.5 fpe.
(https://farm1.staticflickr.com/595/20900058282_3da39db490_b.jpg)
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Hope they work for you Dan.
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I tested today the .251 and .250.
I did not adjust the power on the gun. I shot tethers at 2350 psi. This what giving me 815fps with the 58.4g slugs. That's 86fpe. and I only have 2 turns in with the power adjuster.
No I shot from 40 yards:
8 shots with .250. There are 4 shots in the bottom group
(https://farm1.staticflickr.com/698/20750104469_0bb6131167_b.jpg)
5 shots with .251
(https://farm6.staticflickr.com/5630/20927104822_79096e3c18_b.jpg)
One thing to notice. I have to get used to holding the gun. It has a bit of recoil from the hammer. I bet I can do better with both groups. I'm just wondering what size to order from Tom. The .250 shot a little faster but they opened up a bit.
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Not bad Dan. I would order the mold in .251 and get a sizer if you need it.
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Would you mind sharing your 3D prints? I have 2 top end 3D printers here at the shop.
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If anyone is interested in my SST you can order them from Shapeways.
load from the left:
http://shpws.me/IZSa (http://shpws.me/IZSa)
load from the right
http://shpws.me/IZS8 (http://shpws.me/IZS8)
I made a little money on them so I can pay for prototyping.
As far as the barrel/bottle band. This is specific for WAR bottle Kit and ½ barrel with carbon sleeve. It will only work in that configuration.
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hey glad to see that they are working out for you
let me know what the final results are
mule
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Today I measured the ballistic coefficient of the BBT .251 58.4 grain.
I took 5 shots at each distance.
Gun filled to 2600psi
At the muzzle: 838 fps avg - 91.1fpe
27 yards away: 825 fps avg - 88.2 fpe
the BC came out to be. .2308
I have no idea if this is right or not. I use used chairgun to calculate it. It Seams a bit high but does are the number.
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It does seem a bit high...from the NOE description of a 55 gr, .224 small flat point its estimated BC is .181. That is probably super-sonic and a 40 gr running at 1070 is about .094. I recall a discussion of number crunching and a very small difference in the velocity gave a very different BC.
So, IOW, I have no idear why the number is so high...
cheers,
Douglas
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Thinking about it my chrome way tilted some I wonder if that had to do anything with it. The front was a little lower that the back. That is the only thing I can think of that my give a different reading. I'll try tomorrow again.
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I did some playing around with numbers and just a couple fps difference and the numbers will change drastically.
I think I need to increase the distance and do and average of 10 shots each. I wish I had two Chronis. Also get the sensor close to parallel to the tragectory.
I hope this would help
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Although 25 yards will work well with pellets to measure the BC, bullets lose velocity at a much slower rate, and so 50 yards would give you more accurate measurements.... A small difference in the velocity will, as you say, make a big difference in the calculated BC.... Also, you must input the correct atmospheric measurements to correct the BC to NTP conditions.... In addition, make sure you are using the G1 Model to calculate the drag....
Having said that, you are right in the sweet spot for the BC, it won't yet be on the Transonic upslope for drag, and the boattail is very efficient in reducing the drag in Subsonic flight.... BC's tend to be higher if you measure them Subsonic than Transonic or Supersonic, so a value of 0.23 would not be out of the question....
Bob
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Thanks bob. I will re do the test once we get a little better weather. Right now is too humid to hang outside. I will take note of all the atmospheric conditions and move out to 40 yards which is the maximum I can do.
But it is good to know that .2300 is not way out of range. Is there a better calculator for BC other than the one in chairgun?
I did put in the correct atmospheric numbers and it went down to .2274