G36 barrels are unique to G36's.
I've shot five or six thousand rounds of .400 Cor-Bons through my G21. Have shot a few hundred through my G30. About the same ballistics as 10mm, but with lots less pressure. I'm using a threaded, compensated Accu-Match barrel for the G21 and for my 70 Series Gold Cup; extended, ported Federal barrel for the G30.