Ok, so all I did was replace the Leather Piston Seal with the nylon Replacement Seal in the QB-57 maintence kit. http://scopesandammo.com/storefront/...pair-kit-p-858 I did not change the Mainspring. I sanded the Nylon Seal around the edges a bit so it was smoother fit. (Still nice and tight though.) Here are the numbers:

Crosman - Domed - 7.8 gr - 572 fps
Premier - Hollow Point - 7.8 gr - 579 fps
Gamo - Red Fire - 7.8 gr - 571 fps
Crosman - Penetrator - 8.5 gr - 510 fps
Stoeger - X Speed - 5.56 gr - 600 fps
Predator - Polymag - 8 gr - 548 fps
RWS - Hyper Velocity - 5.2 gr - 680 fps!
Gamo - Lead BB - 8.18 gr - 474 fps
Diablo - Jumbo Monster - 13.43 gr - 379 fps

The same mod might also could have been done by simply cutting 1/4" off the original Leather Seal. The gun fires way smoother now and it is easy to cock as well. Gonna paint the polymers olive drap and call it a night. (post a pic in the gallery) Anyways, hope this info was good for the forum. See you on the next mod.