Quote Originally Posted by Scubashot View Post
Has the new piston seal had an opportunity to bed in?
After fitting a V Mach kit (including a new spring and seal) to my 1987 HW77 0.22" rifle the power was way down, even with all the preload washers installed.
As the seal bedded in the power just kept climbing. I had to remove all of the preload washers and collapse a coil of the spring to keep it legal. Even now I have to keep an eye on it and have had to reduce the thickness of the top hat to fine tune the power level.
I had the same as you with my 177 77k, Had to remove all the washers in the end but lucky enough its settled to about 11.2