Piston orings

[32:1]

yeah, 2fp down is about right.

26 x 67 compares with an hw99, 26 x 71, but it's generally agreed that 10.5 ish is the max for a nice shooting .177 99. I had one that was still sweet at just over 11, but that's pushing it. (yeah I know with a bunch of tuning you can push that a little, I'm talking generally)

you are 4mm stroke down, so it feels like 9 - 9.5 FP is about right for that powerplant.

Things you can do to help a shorter stroke setup make more power:
- lighter piston, to accelerate faster ( but I'd not go less than say 180g)
- Stiffer spring to get faster initial piston acceleration
- try and wring a bit more stroke out of it

Also, what are the transfer port dimensions ?

Excellent ��

The Cometa piston is only 150g with the seal so quite light

So with volume that critical I think it’s why I see the HW seal making a bit less power as it’s a few mm taller.
Not sure I can get more as cocking slot shows very top of piston, I’ll get a couple of different springs and make the nose from brass, I did have a small piece but forgot the measure twice cut once rule ������