The M203A1 is a 40mm, single shot, breech loaded, pump action, shoulder fired grenade launcher. It is used by both American and Canadian forces. It is mounted under the barrel. It ranges from 100-400m adjustable in 50m increments. The most commonly used rounds are smoke, CS, and HE rounds. It weighs 1.3kg unloaded and 1.8kg loaded depending on the round. It is simple to operate, take apart, and clean.
A grenade launcher usually attached to the bottom of an M-16 or M4 assault rifle. More commonly known to Soldier of Fortune 2 players as the n00b cannon due to the fact it is easy to use and can frag a player in one shot, hence it is a favourite among n00bs.
Shiiiiiit! I just got fragged by that n00b and his M203 n00b cannon.