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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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There IS an issue with aluminum and stress that needs careful attention.

December 1 2011 at 11:47 AM
L D  (Login lhd)
Crosman Forum Member
from IP address 75.104.108.22


Response to Using aluminum for pump tube?

Unlike steel, which normally will not become permanently stressed at load levels significantly below the threshold where some stretching begins to show up, even with many, many repetitions of the stress, aluminum has no such threshold, and can become fatigued by such repeated stress, even at levels lower than the point where permanent deformation would have occurred in virgin material.

Some common aluminum alloys, such as 6061 are more prone to this situation than say ... 7075, but the issue needs to be taken into account if many (thousands) of cycles that might approach the listed tensile limits are anticipated.

The T6 spec is a heat treat condition that gives much more strength due to an artificial aging effect. Part of this treatment is a soak at the quite low temp of around 325 degrees. I'm not expert at this, but suspect exposure to much higher temps might negatively affect the heat treat rating.

Not to say don't use aluminum, but just to say do the research and testing first.


    
This message has been edited by lhd from IP address 75.104.108.22 on Dec 1, 2011 11:50 AM


 
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