A hollow point on a 5.56 round .... at least the military round, is not that effective. The existing round is designed so that much of the weight is the rear of the bullet. When combined with a slow twist rate, this creates a situation where the round is designed to tumble. The length of the 5.56 during a tumble is greater than the surface area of a hollow point in the same size round.
"When combined with a slow twist rate, this creates a situation where the round is designed to tumble. The length of the 5.56 during a tumble is greater than the surface area of a hollow point in the same size round."
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Good point. Yet the round tumbles only when it hits something, as does a perfectly-spiralling football in mid-air. Some people think that the original M16A1 rifle made the rounds tumble as soon as they left the muzzle. But I remember pulling the targets at the rifle range on Parris Island in 1980 at 500 yards. The rounds made perfect small holes hitting the paper, and kicked up at least a foot of dust when they hit the sand pile behind the "butts".