GTA
All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: Big-dave0207 on November 01, 2022, 05:56:40 PM
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Can anyone help me please.
.25 p15 lack of power.
5mm tp and barrel to match and all polished
Lane regulator set at 140bar
Reduced exhaust valve spring
Problem is should be sitting around 45fpe but only getting 15-16fpe.
Using jsb exact king heavy diablo 2.20g 33.95gr
Shot string fps
439
449
443
443
443
448
441
442
446
447
This is with a 3mm spacer in the hammer plus a key to compress the spring. Hammer spring is 45mm long.
I bought a trobb hammer and longer spring combo but with both in it was worse.
Shot string with trobb longer spring and new hammer
282
295
291
289
299
Anyone any ideas how to get this thing shooting around 800fps which technically should be factory standard level
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Hmm, strange! I wonder if your lane regulator is somehow not set like you think? There isn't a reg gauge on that p15 is there?
Still even at 100 bar you should be getting better than that.
Has it always been low power since you bought it? Maybe the barrel collar with the port hole is not machined right so the set screws are in the wrong place and the port is not lined up properly?
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Other thought would be a bad or missing bolt / breach seal ??? even then should not be so low. :-\
... or hammer binding and not delivering a full blow ???
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how's barrel accuracy?
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Thanks for the replies. I'm going to tesr the gun down again tomorrow and check all ports line up correctly.
The barrell accuracy is grand just pellet drastically drops over 20m. I don't think the hammer is binding on anything as I stripped it down and polished both hammer and where the hammer chamber is as well.
How would I check that the vertical hole from tp to barrel is aligned?
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Hmm, strange! I wonder if your lane regulator is somehow not set like you think? There isn't a reg gauge on that p15 is there?
Still even at 100 bar you should be getting better than that.
Has it always been low power since you bought it? Maybe the barrel collar with the port hole is not machined right so the set screws are in the wrong place and the port is not lined up properly?
There's no reg Guage on it unfortunately but it's a brand new reg asked to be set for 140bar and I've not had issues before with lane regs.
Yeah it's always been low on power and I thought it was the reg so that's why I upgraded. I can increase the hammer spring until it doesn't cock then back off a bit and that was the max fps I could achieve.
I've even reduced the exhaust valve spring thinking it was too heavy and when it was compressing it was very restrictive for the airflow.
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Lol my old p15 .25 started out shooting cloverleaf pattern at 15yards. Ya might want to cut the distance to 10m and check that accuracy. Orignal barrel was trashed.
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Lol my old p15 .25 started out shooting cloverleaf pattern at 15yards. Ya might want to cut the distance to 10m and check that accuracy. Orignal barrel was trashed.
I will certainly be checking accuracy once I can find ans fix the lack of power issue. Just one step at a time 😀
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If you pull the barrel out with the collar on and look at the set screws divots on top and make sure they are directly vertical of the port hole. If that is good then make sure and remove the set screws in the top of the breech and when you slide the barrel and collar into the breech make sure the set screw divots are visible in the set screw holes and lined up. It's possible the factory stuck it in crooked as well and didnt line things up.
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What Wes said is completely accurate in my view but I will try and say it a slightly different way. There are at least two ways for the barrel port to be obstructed. One is if the divot on the top of the barrel is not vertically above the barrel port. I believe on your P15 the divot will be a bit ahead of the barrel port, on my P35 is is almost right over it. But my P35 barrels have the P15 port too and yours may have the one for the P35. But in any event, checking to see that the divot is correct is where I would start.
The other thing to check would be whether the barrel is installed with the set screw in the divot. You'll have to check that as your remove it or when you reinstall it. If you loosen the set screw and slide the barrel directly out, you should be able to tell. There may also be a mark from the screw on the barrel if the set screw was tightened against the barrel instead of in the divot. The barrel has a couple O-rings on it so sliding it straight out may be a bit difficult, I usually twist side to side some to loosen things up. Putting it back together with the set screw for sure in the divot and then seeing what your velocity is would be the other way to check this. If you loosen the set screw and then tighten it against the barrel, noting the revolutions required and then tighten it again when you think the divot of the barrel is under the screw it will tell you if it really is. More rotation of the screw will be required. If you are slightly off the screw will also rotate the barrel slightly to align. My guess is this is the issue.
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What Wes said is completely accurate in my view but I will try and say it a slightly different way. There are at least two ways for the barrel port to be obstructed. One is if the divot on the top of the barrel is not vertically above the barrel port. I believe on your P15 the divot will be a bit ahead of the barrel port, on my P35 is is almost right over it. But my P35 barrels have the P15 port too and yours may have the one for the P35. But in any event, checking to see that the divot is correct is where I would start.
The other thing to check would be whether the barrel is installed with the set screw in the divot. You'll have to check that as your remove it or when you reinstall it. If you loosen the set screw and slide the barrel directly out, you should be able to tell. There may also be a mark from the screw on the barrel if the set screw was tightened against the barrel instead of in the divot. The barrel has a couple O-rings on it so sliding it straight out may be a bit difficult, I usually twist side to side some to loosen things up. Putting it back together with the set screw for sure in the divot and then seeing what your velocity is would be the other way to check this. If you loosen the set screw and then tighten it against the barrel, noting the revolutions required and then tighten it again when you think the divot of the barrel is under the screw it will tell you if it really is. More rotation of the screw will be required. If you are slightly off the screw will also rotate the barrel slightly to align. My guess is this is the issue.
Just looked over my p15 and there are no grub screws in the breach to hold the barrel in not even threaded holes. Just blank on the top. There's only one grub screw and that is on the scope rail. Is this normal?
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I think I've found the problem....Hammer spring is too weak to open the valve. Dropped the cylinder pressure to 130bar and done a string of shots I managed to get 700fps at around the 100bar mark. So now I need to find a spring to open the valve at 140bar as that's what the reg is set to.
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I don't own a P15 but I watched a youtube where they showed the grub screw for the barrel under the scope rail. I think you have to remove the scope rail to see it. With it loosened (or removed) it should be fairly easy to slide the barrel out. The only resistance would be the two O-rings.
I don't know if you need a new spring or not but I'm glad you found a way to get velocity up. It does sound like the spring may be an issue. McMaster Carr is one source of springs, they have quite a few.
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Back when we were all hotrodding our P15’s I had to build my own hammer and harden it. My gun is a .25 and I shoot it a 150b. Built the hammer to accept American springs. My gun has unobtainable cnc parts and a TJ barrel. Its still not a 33.95gr pellet gun. Try to find a Gauntlet spring if you can. It might cure your ill.
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Oh, leave the stock valve return spring in the gun. If you don’t your ES won’t be as tight as it should be. The minuscule velocity gain isn’t worth it.
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(https://i.postimg.cc/pLz1DS8c/26.jpg)
Modified mine to take an Impact spring and in turn a brass spring guide.
Made for all the difference in the world.
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(https://i.postimg.cc/pLz1DS8c/26.jpg)
Modified mine to take an Impact spring and in turn a brass spring guide.
Made for all the difference in the world.
That looks the part. What's the fx spring size wise in comparison to the standard spring if you could take a pic side by side.
On anther note I finally sourced the problem of my lack of power..... lack of hammer force!!
I managed to construct a heavier hammer spring from 2 Stiffer ones (it's crude but helped me figure out the issue) the reg is set at 145bar and I just couldn't get the valve open enough. But once it came off the reg the fps shot up to 780 so I pulled out the reg and lowered it to around the 130-135bar and not getting constant 760fps ideally wanted to hit the 800fps but as it stands it's shooting as I like for now. Just trying to source an external plenum and may even change for a longer barrel. Thank you everyone for the comments and help. It's great as usual.
P.s anyone know anywhere to get an external plenum for a p15 or have the drawings to machine one that would be great.
Regards
Dave
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The last external plenum I bought came from xtremeairguns in South Africa. pricing was fair and shipping didn't take too long.
IMO, my preferred route to go on a .25 P15 pellet shooter is not to add hammer weight and/or stiffer springs.....but to maximize hammer stroke and make the valve easier to open....
Hammer stroke----You may find stem protrusion to be a bit excessive and have room to trim off approximately .5-1mm. With the P15's short hammer stroke and light hammer, every little bit of travel helps. Be careful though, if you go with too little stem protrusion you will bounce the hammer off the valve and thus make very little power.
Make valve easier to open---The OEM poppets I've seen are significantly oversized, making the valve harder to open than it has to be for the P15's relatively small throat diameter. Reducing poppet diameter to just over the valve throat diameter (while leaving sufficient sealing margin) will help. I've done this with the OEM poppet but ultimately started making my own poppets out of peek.
Combining a peek poppet, sized just barely over throat diameter, and a 2mm stem will allow you to make the valve easier to open AND increase flow. With this combination you will find the OEM hammer spring to have more than sufficient preload even at reg settings upwards of 150 bar.
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The last external plenum I bought came from xtremeairguns in South Africa. pricing was fair and shipping didn't take too long.
IMO, my preferred route to go on a .25 P15 pellet shooter is not to add hammer weight and/or stiffer springs.....but to maximize hammer stroke and make the valve easier to open....
Hammer stroke----You may find stem protrusion to be a bit excessive and have room to trim off approximately .5-1mm. With the P15's short hammer stroke and light hammer, every little bit of travel helps. Be careful though, if you go with too little stem protrusion you will bounce the hammer off the valve and thus make very little power.
Make valve easier to open---The OEM poppets I've seen are significantly oversized, making the valve harder to open than it has to be for the P15's relatively small throat diameter. Reducing poppet diameter to just over the valve throat diameter (while leaving sufficient sealing margin) will help. I've done this with the OEM poppet but ultimately started making my own poppets out of peek.
Combining a peek poppet, sized just barely over throat diameter, and a 2mm stem will allow you to make the valve easier to open AND increase flow. With this combination you will find the OEM hammer spring to have more than sufficient preload even at reg settings upwards of 150 bar.
Nice to see you mackeral5 you still shooting those powerhouse valves?
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The last external plenum I bought came from xtremeairguns in South Africa. pricing was fair and shipping didn't take too long.
IMO, my preferred route to go on a .25 P15 pellet shooter is not to add hammer weight and/or stiffer springs.....but to maximize hammer stroke and make the valve easier to open....
Hammer stroke----You may find stem protrusion to be a bit excessive and have room to trim off approximately .5-1mm. With the P15's short hammer stroke and light hammer, every little bit of travel helps. Be careful though, if you go with too little stem protrusion you will bounce the hammer off the valve and thus make very little power.
Make valve easier to open---The OEM poppets I've seen are significantly oversized, making the valve harder to open than it has to be for the P15's relatively small throat diameter. Reducing poppet diameter to just over the valve throat diameter (while leaving sufficient sealing margin) will help. I've done this with the OEM poppet but ultimately started making my own poppets out of peek.
Combining a peek poppet, sized just barely over throat diameter, and a 2mm stem will allow you to make the valve easier to open AND increase flow. With this combination you will find the OEM hammer spring to have more than sufficient preload even at reg settings upwards of 150 bar.
Nice to see you mackeral5 you still shooting those powerhouse valves?
Hi Mike... nice to hear from you. Very little shooting as of late, when I do it is mostly my 12fpe Prod based guns along with the P15. My big bores have been sitting idle for quite some time now.
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I have three P35s which are very similar to P15s. They are in 177, 22 and 25. I should disassemble them to check but I've seen comments on the Artemis facebook page that the transfer ports are all the same size. That would make the 25 pretty small for the caliber. I'm currently happy with my 25 tuned to low 30s fpe but if I ever decide to turn it up, I will definitely investigate the transfer port size. I got a few more fps by removing a burr from the barrel port.
I have not throughly investigated it but I've seen adds for a larger plenum made by a spacer in the air tube. I think that is how the stock plenum is made. It sacrifices air storage a little but it seems like it would work.
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(https://i.postimg.cc/K8hCj58d/1.jpg)
A few of the Artemis guns share the same basic principle. In the case of the actual valve housing and poppet, comes down to like the same thing no matter which model.
Sorry to say, within reason, there´s not all that much material to hog out either - don´t ask me how i know. ;D
That there in the pic is the 12fpe exhaust port i believe.
On the plenum matter/issue.
No.
The by far wisest move here in my opinion is to add an extension to the tube/tank. As the regulator resides within the tube already an extension bolted between the main block and the tube will become added plenum volume and in essence.. pick your poison as far as capacity. Threads are common metric btw. (M16 if memory serves? Been a while..)
On the actual valve housing though. You get to a point where the natural solution will be to ream out the cutout in the main block and turn a fresh housing of greater diameter. The stock piece, out of brass, will only cope that far and if we´re into 25cal... hello.
I guess what i´m saying is that i believe it might be a wise option to simply come to rest in that the P15/35/M-16 aso MIGHT be the ones to just run at elavated reg pressures.
At least if higher power figures is your game. Port dimension much beyond 6,5mm and you´ll "hit water" so to say. IOW, keep it to 6mm to stay safe.
That bad?
Well. An idiot like me could always go ape with the heavy machinery and redesign the entire thing. This is not for all though, out of obvious reasons.
Port beyond 6mm diameter.. you´re pushing it.
Also be aware that the Artemis guns that run on this... shall we call it "brass valve housing" setup, it is imperative to see to that the o-rings for the housing are in tip-top shape and pulling their fair share.
When i service these guns it´s real common to get the housing out with ripped or otherwise damaged rings. More common than not actually.
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The last external plenum I bought came from xtremeairguns in South Africa. pricing was fair and shipping didn't take too long.
IMO, my preferred route to go on a .25 P15 pellet shooter is not to add hammer weight and/or stiffer springs.....but to maximize hammer stroke and make the valve easier to open....
Hammer stroke----You may find stem protrusion to be a bit excessive and have room to trim off approximately .5-1mm. With the P15's short hammer stroke and light hammer, every little bit of travel helps. Be careful though, if you go with too little stem protrusion you will bounce the hammer off the valve and thus make very little power.
Make valve easier to open---The OEM poppets I've seen are significantly oversized, making the valve harder to open than it has to be for the P15's relatively small throat diameter. Reducing poppet diameter to just over the valve throat diameter (while leaving sufficient sealing margin) will help. I've done this with the OEM poppet but ultimately started making my own poppets out of peek.
Combining a peek poppet, sized just barely over throat diameter, and a 2mm stem will allow you to make the valve easier to open AND increase flow. With this combination you will find the OEM hammer spring to have more than sufficient preload even at reg settings upwards of 150 bar.
Thanks for the advise. Ive emailed xtremeairguns but heard nothing back yet.
Any idea what the length is of the OEM hammer spring is as mines sitting at 45mm. It's a 2nd hand rifle and not a clue if it's been played with or not.
Yeah to me the poppet is huge but didn't what to touch that incase I messed up the seal. I reduced the poppet spring to make it easier to open.
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Racing,
Thanks for your many posts on this forum with your "out of the box" thinking!Figuring out ways to make something work better is how many innovations come about, keep up the great work!!
John