Regarding Gatling guns:
Tippmann (yes, the company that used to make the .22 and .17 MG repros and then paintball guns) now makes one that runs 9mm using Glock mags.
Tippmann (yes, the company that used to make the .22 and .17 MG repros and then paintball guns) now makes one that runs 9mm using Glock mags.