The M4 has a short, 14.5-inch barrel with an overall length about 10 inches shorter than the M16A4. It weighs in at just over six pounds, a pound lighter than the rifle. The shorter barrel does sacrifice some muzzle velocity, meaning a slightly shorter effective range. But in close-quarters battle, that is rarely a factor, and each Marine fire team already has an M27 Infantry Automatic Rifle, which in semi-auto doubles as a designated marksman's rifle. That role will no longer be filled by the Squad Advanced Marksman Rifle, a match-grade M16 with a scope.