"M4A1 assault rifle. The gun is set in MANUAL/AUTO mode. It uses 5.56mm NATO rounds."
A quick firing rifle that can be used very nicely on most creatures. It is tailored for use where light weight and quick action are required. The gun runs on a % counter which goes down from 100% (or 100 bullets). Clips you can get each have another 100% ammo.
You can use the M4 in Easy mode with both Jill and Carlos as their starting Weapons. In Hard, Carlos uses it as a Starting Weapon still and Jill can earn it by defeating Nemesis seven times. It is also a weapon you can earn with unlimited ammo from the Mercenaries mini-game.
Realistically, the stock is collapsible for compact storage and operations and the Colt M203 grenade launcher can also be fitted for increased firepower. It's a shame that Capcom didn't give Carlos or Jill the ability to use an add on like that.