I'm no expert, but some of the shooting is in salvos... About 10 to 15 shots, but there are protracted discharged shootings where the rounds run to easily over 40 rounds. Perhaps way more.
A converted semi automatic would allow the 10 to 15 rounds, but 40 rounds plus would need ammunition on a belts, in an automatic weapon.
Military styled machine guns.
i.m.h.o.
