To answer the question of 1 caliber I would take my G19 and 15rd and 33rd mags. I don't have a 9mm carbine or rifle so instead I'd take a supressor for the Glock. If I could take stuff I don't have the P90 and pistol combo sounds good for volume of fire power. And if I could take multiple calibers I'd take the Glock and M@P15T ideally both suppressed. Possibly the USP45T as well.