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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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Final setting

June 27 2012 at 7:58 PM
robert  (Login gubb33ps)
Crosman Forum Member
from IP address 68.105.50.68


Response to Transfer port restrictions

OK...with a goal of 12 foot pounds and a tiny air volume of an estimated 44ccs, kept playing with the transfer port. Striker hit was running the carbine at 160-110BAR (or about 2350 to 1600psi.

Changed the tension UP a little bit (one pre
tension turn of the screw), swapped for a striker that was 10gr. Lighter, and changed the transfer port to .072 ( 5/64ths).
[IMGhttp://i157.photobucket.com/albums/t50/ribbonstone/Hip Ac/DSCF1899.jpg[/IMG]

14.3gr. Benjamin Cylindrical

581
597
601

606
613
620
623
628
628
625
624
618
614
606
608
607
610

596
597
579

Which works out to:
25 feet per second = 628 603= 14 shots

So... 2350-1600 fps...44cc....20 shots...601fps average...call it a BAR/CC-FPE of about 10.

Just saying.

Is not a great long shot count, but it has a dinky air volume.
Efficiency of 10 is pretty good for a 12 foot pound gun (OK..call it 11.5 to 12.5 gun).

Suggestions:

1. Restrictive transferor port is USELESS if looking for maximum velocity.
2. The increase in shot count with a strangled down transfer port is VERY CLOSE to the same energy x shot count of a wide open transfer port...it just doles out the energy over a long time frame.



 
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