Shouldn't make a difference what stock you have. As its only the tube that is being switched out.
Also a 12V with a m120 spring may cause heavy damage to the gearbox if used on full auto. So a safer bet would be a 8.4V large battery, a 9.6V small/large battery or lipo.
Originally Posted by Crunchmeister
Imagine ads for semen restaurants. I can see it now... "Come to Seminal Sam's, where you can eat loads without blowing all your wad..."