i use a lipo internally on my upgraded mp7... actually i should say used to since i accidently killed the lipo while cleaning my room and haven't ordered a new one. I wouldn't actually plan on using it without upgrades though because of the obscene discharge rate that some lipo's have. When using it before upgrades the gearbox would cycle faster than the mags could load. sure it was fun to fire, but i would run out of ammo so fast
