I've been playing about with a mk 6 .177 for a good while now. I've done just about everything it's possible to do with one. It was in quite good nick, so thought it was worth working on. Totally reworked internals and can't get it to do over 8.5 fpe. Advice is: if your going to spend a lot of money, time and effort on it, don't expect miracles. It ain't going to happen.