More Chrono Data - using 392 mod todayAll 8 pumps - no air left overCrosman PHP 14.3gr - 695 fpsGamo TS22 21.75gr - 595 fpsH&N Rabbit II 25.62gr - 551 fpsGamo Round Lead BB 15.43gr - 704 fps
The hole for the valve bolster is directly across from port into the barrel.
FWIW....after many learning experiences over past few years, I was able to get to 650.5 avg. with 8 pumps.That’s 17 ft/lbs measured on beta chrono. That’s with JSB 18 gr. However compression o-ring developed a leak and have just replaced with Buna n-70 rings..Last were stock Crosman. Usual mods of 1/4 off inlet check valveand remove 2 threads. I found headspace,volume and porting most critical. Took exhaust port to 5/32 in valve and barrel and relieved sharp bend internally..Using stock hammer and valve springs. Two other items though: Was older valve without Delrin exhaust valve so installed one from Mac1. Cut a 45 degree seat and lappedin with bore paste on my brothers lathe.Kudos to Crosman on changing their exhaust valve. That added a little more volume and improved air flow. Also ground seat (very tedious) around valve exhaust port and supergluedO-ring in.Does have solid billet pump arm. I like shooting this gun so much I wanted to upgrade but not HAVE to pump it so much. Really love where it’s at now. Really performs at even 6 pumps. Hope this helps !
Quote from: Creaker on March 22, 2019, 09:14:22 AM FWIW....after many learning experiences over past few years, I was able to get to 650.5 avg. with 8 pumps.That’s 17 ft/lbs measured on beta chrono. That’s with JSB 18 gr. However compression o-ring developed a leak and have just replaced with Buna n-70 rings..Last were stock Crosman. Usual mods of 1/4 off inlet check valveand remove 2 threads. I found headspace,volume and porting most critical. Took exhaust port to 5/32 in valve and barrel and relieved sharp bend internally..Using stock hammer and valve springs. Two other items though: Was older valve without Delrin exhaust valve so installed one from Mac1. Cut a 45 degree seat and lappedin with bore paste on my brothers lathe.Kudos to Crosman on changing their exhaust valve. That added a little more volume and improved air flow. Also ground seat (very tedious) around valve exhaust port and supergluedO-ring in.Does have solid billet pump arm. I got mine from Mac 1 with the link attached to the arm as I recall. Not sure if He sends them out that way now or diy. As far as the handle rolle pins go, you drill through the center with a 1/16 (check size) til out the other side and follow back with drill same size as pin,then can be driven through without messing wood up hopefully too much. Got that from Tim at Mac1 I think. But not certain. Makes a world of difference in Feel of gun and highly recommend for longevity. As long as it holds together,the original pump arm probably has same potential for performance but solid billet just feels great,especially at higher pumps. Hope this helps!1 I like shooting this gun so much I wanted to upgrade but not HAVE to pump it so much. Really love where it’s at now. Really performs at even 6 pumps. Hope this helps !Creaker,I also wish to put in a solid pump arm and lever link, but how did you remove the old one ? Did you replace the link too ? On the pump are there is only one side where the spring pins are pushed through the stock, what is the best way to remove the pins ? How much extra quality do you feel this gives the gun in terms of wear/toughness and does the extra rigidity add anything to the velocity you think ? ?Thanks Creaker !wll
FWIW....after many learning experiences over past few years, I was able to get to 650.5 avg. with 8 pumps.That’s 17 ft/lbs measured on beta chrono. That’s with JSB 18 gr. However compression o-ring developed a leak and have just replaced with Buna n-70 rings..Last were stock Crosman. Usual mods of 1/4 off inlet check valveand remove 2 threads. I found headspace,volume and porting most critical. Took exhaust port to 5/32 in valve and barrel and relieved sharp bend internally..Using stock hammer and valve springs. Two other items though: Was older valve without Delrin exhaust valve so installed one from Mac1. Cut a 45 degree seat and lappedin with bore paste on my brothers lathe.Kudos to Crosman on changing their exhaust valve. That added a little more volume and improved air flow. Also ground seat (very tedious) around valve exhaust port and supergluedO-ring in.Does have solid billet pump arm. I got mine from Mac 1 with the link attached to the arm as I recall. Not sure if He sends them out that way now or diy. As far as the handle rolle pins go, you drill through the center with a 1/16 (check size) til out the other side and follow back with drill same size as pin,then can be driven through without messing wood up hopefully too much. Got that from Tim at Mac1 I think. But not certain. Makes a world of difference in Feel of gun and highly recommend for longevity. As long as it holds together,the original pump arm probably has same potential for performance but solid billet just feels great,especially at higher pumps. Hope this helps!1 I like shooting this gun so much I wanted to upgrade but not HAVE to pump it so much. Really love where it’s at now. Really performs at even 6 pumps. Hope this helps !
To remove old,take front rolle pins out and then slide link and piston to where it lines up with one of the holes where you just removed the pins. Then you can push out the pin that connects link to piston assy. Then just slide piston out. Assemble reverse. The stock pins can be drilled through the center til out the other side of stock. Then chase back to pin with larger drill to pin using small hole as guide. Then the pin can be driven through. Believe got that from Tim at Mac1 on a post.Not sure. 1/16 and 1/8 bits I think,but double check.This has worked well for me. Solid billet and link definitely upgrade the gun as far as feel and longevity.Can highly recommend. As far as performance,a pump is a pump. But at higher pumps a lot of strain on original parts. They will tend to flex some. Mine from Mac1 came with link attached. Not sure if he still sends them that way or diy now.Great guy though I’ve not met him. Reminds me- got get some more “secret sauce”. Hope this helpful. PUMP IT!
I understand your concern about having holes on the other side. But they are in pretty tight and that’s good because after all the pumping they usually keep everything tight. Least never heard complaints of them loosening. I guess might be possible to pull them but don’t have anything to offer on how to get that much purchase on them to get them out. Trying to get ahold of the outside is about impossible without making a mess of the stock. I settled for the above method and didn’t get any chips,just have holes that match the other side. Given the ID of these pins it’s hard to imagine a tool that could pull them. Anything that screws in would probably expand the pin and make it more difficult. But I learned long ago I’m not the sharpest tool in the shedand maybe there is a way I don’t know or somebody will invent one! Best of luck on your build though. These are great little guns-light,balanced and powerful enough.It may be a bit of a journey but sweet when you get it where you want it.
Advertise Here
Share This!