Isn't that bigger then the gun mounted on an A-10 Warthog?
Yes, but he's a big guy and he brought to really big fat chicks along for bracing.
Yep, that's a 30mm. 38 mm is only 5% less than the 40mm "ack-ack" guns common during WW-II on ships. (Still used too, on the AC-130 for example, but not as common)