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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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crosman 357w 6" barrel

June 30 2012 at 4:29 PM
john  (Login mac1911)
Crosman Forum Member
from IP address

Ok so my first outings with this thing wasn't great. Inconsistant groups and velocity. Gamo wad cutters seemed to do the best and can hold 2.5"@10 paces when I'm doing my part. Velocity is another story out of the box out of 100 rounds only the 1st shot on fresh powerlet would even approach 400fps. And it was all over the place. I decided to modify the mag a bit. Sanded the forward face of the mag flats 220,400,600 paper. This seamed to help as velocity now creeps into 400s more often plus I was getting misfires. I decided to try and chamfer the pellet holes on the rearward face of mag. Bingo this brought velocity way up but the spreads where even higher. This did seem to stop the misfires except very fast trigger pulls.
Now I noticed several of the pellet holes in the mag are tighter than others. For a short fix I coated several pellets in tooth past and passed them through the mag many times.
So test went on like this. Ten shots 10 missip between shots.
one mag was loaded till pellets where flush with rear of mag.
H vel 446fps L vel 396.7 spread 67.3 average 421.7 much better.
2nd mag was loaded pushing pellets through till flush with forward face. H vel 457.2(6th shot) L vel 394 fps spread 63.2 Av vel 412.4

Can anyone tell me if the velocity is. More affected by the snug fitting pellets vs loose in the mag. Seems I got higher velocity with pellets flush close to valve vs loose fitting pushed into mag.

Also I find it funny that there's always one really high vel. Generally its the 1st shot but not always. If I drop the high and low in each ten shot string I really like the numbers. I don't see a huge difference in grouping any more now that the velocity is behaveing better.

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