Revealing mistake: When we see the new recruits at boot camp, they are wearing M1 Helmets. But if you look closely, they have rivets through the sides of each helmet where the chinstrap bales would be. In reality, the M1 helmet chinstrap bales were and continued to be welded onto the shell of the helmet. This indicates the helmets in the film are probably plastic replicas with the bales being riveted in place.