So another week on the new large style piston.
I had shot over 300 rds through it and probably as many dry shots, but Saturday night the glued in small o-ring blew. so I glued in another and played on Sunday with it. another 300 rds ad still going strong.
A stiff urethane o-ring would fix this, I just need to find one.
As for the balls being pushed past the detent when the gun is cocked, I ran an under bored barrel, so that when it shoots past the detent it wont roll down the barrel before being fired. its not the best solution, but it works for now.
this is what happens when you cock it. MVI_0921.mp4 video by capitalpaintball | Photobucket
When the body was milled for the larger piston they put a chamfer so the o-ring wouldn't get sliced, but this means the piston o-ring leaves the body a fraction of a second earlier then it used to. the o-ring positions on the shaft of the piston are identical to the smaller piston, I think they need to move the o-ring grove back the same distance as the chamfer.
pretty simple fix if you have the skills and equipment(I don't, at least the second part.)
I tried to increase the length of the piston by putting spacers under the head but that didn't work.