Author Topic: 22xx valve mods (Read 39085 times))

rsterne · « **Reply #40 on:** June 01, 2012, 01:25:49 AM »

Quote

If your first 2 shots are really powerful and the third is approximately on par, maybe You need less hammer spring. Your flow may be so high that all your potential is going into the first two shots.

I agree....

Bob

alex77147 · « **Reply #41 on:** June 01, 2012, 01:30:16 AM »

Quote from: Bill G on May 31, 2012, 09:34:44 PM

There are diminishing returns with increased dead volume. That's the space between the valve passage and the back of the.pellet. Too much can have negative effect on velocity. I skimmed through these posts so I may have missed something. If your first 2 shots are really powerful and the third is approximately on par, maybe You need less hammer spring. Your flow may be so high that all your potential is going into the first two shots.

I'm not sure i'm getting you correctly, by dead volume do you mean the area between the exhaust port of the valve and the transfer port of the barrel? And my velocity and muzzle energy is fairly consistent from a 1900psi fill to about 1000psi.

rsterne · « **Reply #42 on:** June 01, 2012, 01:33:23 AM »

The `dead volume`is from the valve seat to the base of the pellet.... The smaller the better, it keeps the pressure up.... but you need enough area to get good flow.... Like everything else, a compromise....

Our comment about the hammer spring was directed at your `phone book`results.... two strong shots followed by a weaker one....

Bob

alex77147 · « **Reply #43 on:** June 01, 2012, 01:43:38 AM »

Quote from: rsterne on June 01, 2012, 01:33:23 AM

The `dead volume`is from the valve seat to the base of the pellet.... The smaller the better, it keeps the pressure up.... but you need enough area to get good flow.... Like everything else, a compromise....

Our comment about the hammer spring was directed at your `phone book`results.... two strong shots followed by a weaker one....

Bob

Ok I see what you are saying now, but I can't replicate those results again. I don't know why those two shots went through and now the pellet gets stuck about half way in the phone book. I had to extend the bolt because most pellets would seat about halfway past the t port as a result some hardly fly out the barrel.

rsterne · « **Reply #44 on:** June 01, 2012, 02:04:16 AM »

I've seen lots of pellets that only about half clear the transfer port.... While you can pick up a few fps if they are just forward of the port, it's not a huge difference.... After all, once the pellet moves, the port is no longer blocked....

Bob

alex77147 · « **Reply #45 on:** June 01, 2012, 02:07:03 AM »

Quote from: rsterne on June 01, 2012, 02:04:16 AM

I've seen lots of pellets that only about half clear the transfer port.... While you can pick up a few fps if they are just forward of the port, it's not a huge difference.... After all, once the pellet moves, the port is no longer blocked....

Bob

Well for me it made a big difference, mostly with a 13gr jsb. What mods have you done to your 2260 to achieve 50fpe?

rsterne · « **Reply #46 on:** June 01, 2012, 12:44:05 PM »

Pretty much everything you can think of.... Bored out valve with bigger, straighter ports, drilled transfer and barrel ports, shortened and slimmed valve stem, enlarged valve inlet ports, power adjuster, heavier hammer spring.... Part of the key to big power is a large plenum between the regulator and the valve (on regulated guns) to keep the average pressure up during the shot.... It will only shoot over 50 FPE with EunJins (ie heavy pellets) when running about 1900 psi.... I have detuned it to 36 FPE with 18 gr. JSBs as that is the best (most accurate) setup for long ranges.... and gives a decent shot count....

My latest version uses just 1600psi and can be found in this thread.... http://www.gatewaytoairguns.org/GTA/index.php/topic,26476.msg240854.html

Bob

alex77147 · « **Reply #47 on:** June 01, 2012, 03:08:21 PM »

Quote from: rsterne on June 01, 2012, 12:44:05 PM

Pretty much everything you can think of.... Bored out valve with bigger, straighter ports, drilled transfer and barrel ports, shortened and slimmed valve stem, enlarged valve inlet ports, power adjuster, heavier hammer spring.... Part of the key to big power is a large plenum between the regulator and the valve (on regulated guns) to keep the average pressure up during the shot.... It will only shoot over 50 FPE with EunJins (ie heavy pellets) when running about 1900 psi.... I have detuned it to 36 FPE with 18 gr. JSBs as that is the best (most accurate) setup for long ranges.... and gives a decent shot count....

My latest version uses just 1600psi and can be found in this thread.... http://www.gatewaytoairguns.org/GTA/index.php/topic,26476.msg240854.html

Bob

Nice build! Pretty much did the same mods as you did minus boring out the valve throat and boring out the valve to clear the poppet. What are you using for your transfer port?

rsterne · « **Reply #48 on:** June 01, 2012, 10:26:03 PM »

Steel Crosman port drilled to 0.166"....

Bob

alex77147 · « **Reply #49 on:** June 02, 2012, 01:45:48 AM »

Quote from: rsterne on June 01, 2012, 10:26:03 PM

Steel Crosman port drilled to 0.166"....

Bob

I got the rifle with a polytube, I should have waited and got a crosman t port.

alex77147 · « **Reply #50 on:** June 02, 2012, 07:10:51 PM »

In the future I was planning on getting a riser breech or a multishot breech, I know the t port would have to be longer. How would a longer t port affect velocity? would it be just a few fps lower or something dramatic?

rsterne · « **Reply #51 on:** June 03, 2012, 01:32:07 AM »

A slightly longer transfer port will only cost a few fps.... The transfer port in an RWS 850 is a couple of inches long and it still develops good power....

Bob

alex77147 · « **Reply #52 on:** June 03, 2012, 01:53:02 AM »

Quote from: rsterne on June 03, 2012, 01:32:07 AM

A slightly longer transfer port will only cost a few fps.... The transfer port in an RWS 850 is a couple of inches long and it still develops good power....

Bob

Ok just wondering, since you mentioned "dead volume"

rsterne · « **Reply #53 on:** June 03, 2012, 06:20:30 PM »

Yeah, the 850 is an anomaly to me.... The amount of dead volume is ridiculous.... Maybe it would be just that much better without it?....

Bob

alex77147 · « **Reply #54 on:** June 04, 2012, 03:39:02 AM »

Quote from: rsterne on June 03, 2012, 06:20:30 PM

Yeah, the 850 is an anomaly to me.... The amount of dead volume is ridiculous.... Maybe it would be just that much better without it?....

Bob

maybe the t port is a lot thinner even though its a couple of inches long? what does an 850 get out of the box in fpe?

rsterne · « **Reply #55 on:** June 04, 2012, 12:39:37 PM »

"Out of the box" it's CO2.... The transfer port is 4mm full length (0.157")....

Bob

alex77147 · « **Reply #56 on:** June 06, 2012, 08:51:04 PM »

update

installed a .041 hammer spring, getting 699fps with 25.4gr pellets. still not 40fpe I am hoping for.

alex77147 · « **Reply #57 on:** June 07, 2012, 03:31:29 AM »

another update

redid the transfer port, wrapped the poly tube in some thread sealant tape. Shot a jsb 25.4 pellet now getting 779fps or almost 35fpe! I must reach 40+fpe!

lloyd-ss · « **Reply #58 on:** June 07, 2012, 07:21:19 AM »

Sounds like you are getting back on track now. An 80 fps increase must have been either a pretty big leak, or the poly tubing was installed in such a way as to have been partially blocking the transfer port.

rsterne · « **Reply #59 on:** June 07, 2012, 01:15:54 PM »

Quote

I must reach 40+fpe!

I've re-read this thread, and I can't see where it says what barrel length you have or what main tube you are using.... Is the barrel a 24"?.... Is the main tube from a 2260, or a shorter one from a 2240 or 2250?.... All of those things have a big affect on performance.... Are you still running 1300-1400 psi?....

Bob

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22xx valve mods

Author Topic: 22xx valve mods (Read 39085 times))