Can a heavy piston rob power?

[Shed tuner]

So I guess the simple answer is that a heavy piston doesn't rob power unless using extremes

But just for fun I wonder what springer has the heaviest piston, my guess is a Patriot

In a mk1&2 they are too heavy, and that lump should be thrown away. With a suitable replacement spring, it becomes nicer to shoot.
However in the long stroke Mk3, they are need to maintain piston momentum with the much higher swept volume