Seal Size

[gatonini]

A dumb question here how much oversize  should the piston seal be versus the chamber size of the gun in thousandths ?

[LongIslandArcher]

I'm guessing a quarter of 1/1000" since it doesn't have to be too tight in the tube, because if you look at the top of the seal, you'll see a groove between the seal's outer rim and the inner ring that holds it down to the piston's tophat.  Upon firing, the seal's outer rim flares out against the receiver tube because compressed air is forced into this groove.  If the seal's too tight, your gun won't shoot fast, if it shoots at all.