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 photo 63f5b325-0274-4312-9dbd-2effde5b3715_zps0x27orls.jpg

Alan Alford's build

2250b Tube for later move to bulk CO2.
12" .22 Caliber Barrel from Doomsday Backpacker
Brian & Assoc. Alluminum Breech with 2 barrel screws
Original site rear
Pin site on Custom Mt. Airguns Muzzle Break
2x1 Centerpoint Scope with UTG dovetail adapters
Mountain Airguns Custom Bolt and Handle
Mountain Airguns Custom Power Adapter and spring guide
B&A Boss Valve for extra Power

Built mainly for fun and to shoot at local Field Trial Pistol Match.

It currently it shoots a 14.3 Crosman Hunting Pellet at about 530 fps in a 72 degree room for 8.92 FPE.



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Steve. As requested. Here are the piston parts for the testing.

March 10 2012 at 9:54 PM
Phil  (Login Duane30)
Crosman Forum Member
from IP address 74.140.196.166

Here is the piston unit for testing. Mind you, this is a crude way of getting things to work. Not particularly taking a fancy to shaking the gun each end every time to get the piston out. Tried string, but is was getting hung up in the moving parts:
[linked image]

This is the piston seal with the cavity shown. The cavity volume is right at .0007cu.in./.011cc:
[linked image]

The next picture is the valve, again. This particular valve, though the same valve, has been altered at the piston side. If you can see it, there is a pronounced taper to match that of the conical shape inside the piston seal. There is a shelf the same with of the thickness around the edge of the piston to allow sealing contact:
[linked image]

The idea of tapering the valve face was to minimize losses between the o-rig and seal. Then, a well had to be created in the piston seal to allow clearance for the exhaust stem to pop and to act as air storage space. In addition, the well creates a more pliable piston seal wall.



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