Quote Originally Posted by evert View Post
The "Blue book" is never a good source for anything, but I find these velocities for the different version built on this mechanism:
-HW50, made from 1972 until 1995, 700fps
-Different HW55 versions and differing velocities: 590fps, 660fps, 700 fps
-Beeman Rb, madefrom 1983-1997, 720fps

So Tony, your predicted 8 fpe is probably max of what I'll see from the gun with the original piston.

I'll have to shoot dads gun over the chrono to see what it ended up with.
I think it all depends on what kind of firing cycle you want to end up with Evert.

Between 9.5-10.5 ft lbs can be obtained in .177 with a standard piston and synthetic seal but you do need a stiff spring.

While you have yours apart, please can you check whether the transfer port is straight or angled on your 50.

I have a 50 project going at the moment and it took me by surprise to find the transfer port is angled.

All the best

HW55T