Flash suppressors are not new. The very horrible Enfield No. 5 Mk 1 Jungle Carbine, which was issued in World War II, had a cone-shaped suppressor. M-14s have suppressors, even though they have rifle-length barrels. And, of course, every rifle we issue, from the M-16 on forward, has one. They work by rapidly cooling the gas that exits a rifle’s muzzle.