Reply To: Finally figured out velocity loss
With those velocities, I presume your TX is a .22.
It sounds like the new piston seal was so tight it was slowing down the piston travel speed.
re. uniondr’s comment, did you check how smooth the bore is? Maybe polishing the inside of the bore would have been a better way to loosen up the fit. But then, it wouldn’t be a stock gun any more, and you’d be stuck using the bigger seal sizes forever.
This is always the tricky thing about .22 springers. They’re either magnum class (and thus very heavy and harder to shoot) or they’re not shooting fast enough and have a loopy trajectory.