WE glock 18c for full auto, although I have no idea if it's any good
But I will say glock, they seem to be good and thave good rep, not heard much about m9 and so no idea. And there should be lots of upgrades internally and externally
Mack - Good luck with that, they don't last that long. And Army mags are horrendous. The Gas chamber also isn't compatible with anything else, found that out the hard way...after buying a rather expensive TM upgrade one to replace with