the small-caliber 5.56, essentially a .22-caliber civilian bullet, is far better suited for shooting squirrels than the enemy
I presume the Major doesn't care to eat his squirrels.
Head shot man. I shot a squirrel with a bigger caliber than that. Head shot. Easy with a scoped rifle although illegal for hunting. No lead to break your teeth on unless you are one of those who suck squirrel brains.