Ya know, I read all the time about the mods for these guns....what you can get out of them and such.
I only own one. I got it when they first came out as the QB78, shiney stock and all. I have not modified anything on it. It's always shot consistently. In my basement it will continually put one pellet after another into the same basic hole. It seems to digest almost anything I put through it. It has numerous pesty-birds to it's credit over the years.
I know I could get mine tuned to shoot a .22 pellet 750fps and get 25 shots from 2 CO2 cartridges. But I get 50-60 good shots in the 550fps range now (I usually just drop in one fresh cart for 30 good shots). It shoots better then I can hold it, it gets plenty of shots per cartridge, and it digests about any pellet well. I dunno.......I've never had an overwhelming urge to mess with what is already a great shooting gun. Maybe I just got lucky?
Jack