Can a heavy piston rob power?

[look no hands]

The RB does not need any help making power apart from winding out the restrictor screw in the transfer port in the roller breech, I had to take a coil or so off mine after that mod & new breech seals to keep it below 12.....(RB airsporter carbine in .22) felt slammy & not nice to shoot before, improved it no end & it was the best airsporter I ever shot by far & very accurate too with FTT's.

How true yo are, I'm actually confusing the subject by quoting something that isn't connected to this problem, as you say the RB2 doesn't have a problem making power with a heavier than usual piston, JB said that reducing the pistons weight helped with recoil reduction and a smoother firing cycle, I apologise for any confusion caused.