Since my 1322 ws already at the legal limit, I picked up a 760 for $20 and decided to try the "shimmed pump cup mod." Shimmed the cup and supported the raise with a small section of plastic coffee can lid. (7/16" shim, 1/2" support.) Never knowing what to expect with these mods, I tested it out against the "stock" chrony tests and found decreases in excess of 80 - 100 fps! Not a problem as this is all a great learning experience, but being so I can't help but wonder why the decrease? Can anyone shed some light on the fps reduction, when so many claim this mod to be extremely effective?

Thanks.