1377 flat top piston

Posted by - oleo Feb/03/2010 at 10:44PM

Just got my first air pistol ever, crosman 1377. Used to big guns.
Anyway, I flattened the valve and got a brass flat top piston. The
velocity went from 470 fps with 7.9 grain pellet to 565 with 10 pumps. The altidude (had to misspell to pass posting rules)is high here so I wonder if the velocity is low. Does this valve diesel if oil gets into it? I oiled everything before I put it back together. Are you supposed to use fewer pumps? I also pumped it to 14 and got 615, and 15 to get 618. There's a slight amount of air left but not enough to spit out a pellet. After about 20 shots I suppose there is no dieseling, but are there any comments?

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