The UA-55A is the second iteration of the well known model 55 assault rifle made by Universal Arms. Rate of fire is 450 rounds per minute feeding from a 50-round magazine and yes the magazine would have to stick out quite a bit unlike on the pictures below of the MA37 from the Halo series of games. The usable cartridges would be 6x48 and 7x46 respectively and share the same rim diameter of 10.00mm and have the same total cartridge length of 60mm so all you would have to do to change the calibre is to switch barrels. There is also a UA-55B semi-auto only variant that comes with a 20-round magazine which would be the cadet rifle and/or suitable for older children. And finally the latest variant the UA-55C replaces the flashlight with a 50mm (50x40R) single-shot grenade launcher.