"What's this?"
"That's the grenade launcher... I don't think you wanna mess with that."
Ripley and Cpl. Hicks (from Aliens)

The Armat U1 Grenade Launcher is an American-made underbarrel grenade launcher attachment for the M41A Pulse Rifle,[1] M41A Pulse Rifle MK2 and M4RA Battle Rifle and used primarily by the United States Colonial Marine Corps as their standard underbarrel attachment for the M41A and M41A MK2.


The U1 Grenade Launcher comprises a barrel, breech and four-round internal magazine. Grenades must be hand-loaded into the launcher's four-round magazine, which are then loaded into the breech and primed to fire from a pump action.[2]

When attached to a M41A Pulse Rifle or M41A Pulse Rifle MK2, the U1 is fired using a trigger just in front of the rifle magazine, the housing for which doubles as a grip during grenade firing.[2]

The U1 Grenade Launcher was also integrated in the MOX Mark 1 Berserker Unit's arsenal, firing M40 HEDP Grenades,[3] M38 HEAP Grenades[4] and M108 Buckshot Rounds.[5]


The U1 is capable of launching a range of ammunition types:

M40 High Explosive Dual Purpose (HEDP): The most commonly used grenade round for the U1, the M40 round is marked by a red plastic cap. With a muzzle velocity of 87 meters per second, the M40 is accurate up to 180 meters and effective up to 400 meters, and has a casualty radius of five meters.[6] The M40 can also be employed as a timed-fuse hand grenade.[6][7]


M40 HEDP grenade

M38 High Explosive Armor Piercing (HEAP): Marked by a green cap. The M38 has a similar detonation mechanism and casualty radius as the standard M40, but is additionally capable of penetrating up to 7 cm of homogeneous steel before exploding.[6]

M51A Bounding Fragmentation: Marked by a blue cap. The M51A incorporates a small primary charge that, upon impact, propels the larger secondary charge some two meters into the air before it exploding. This airburst detonation is particularly effective against troops in the open or within fortifications without overhead cover.[6]

M108 Buckshot: Identifiable by a flat, black nose. The M108 is essentially an oversized shotgun round meant to provide the user with devastating close-quarters firepower. It has a range of 30 meters.[6]


M108 Canister (buckshot) grenade

M230 Baton: Reserved for civil disturbances and rarely issued to front-line troops, the M230 is a low-velocity plastic projectile used for non-lethally incapacitating or disabling unarmored humans.[6][8]

M60 White Phosphorous Incendiary: Marked by a white cap. The M60 is filled with white phosphorous which, upon impact, spreads up to 15 meters to create a rising smoke cloud and flame. It also has a secondary incendiary effect on vegetation and materiel.[6]

M72A1 Starshell: Marked with an embossed letter 'S' on the cap. The M72A1 is primarily used to provide illumination, generating 50,000 candelas for approximately 45 seconds. It is designed to be fired vertically into the air, where at 200 meters elevation it will deploy a parachute and ignite.[6]

T3 Tear Gas: Reserved for civil disturbances and rarely issued to front-line troops, the T3 is a small tear gas filled canister used for non-lethally incapacitating or disabling unprotected humans.[9]

G2 Electroshock Grenade: Primally used for riot-control, the G2 delivers an electric payload strong enough to paralize a human nervous system.[10]

Prox-Mines: The Prox-Mine is a proximity detonated anti-personnel mine composed of a thermite charge. Once fired, the Prox-Mine will stick to a surface. If any enemies are detected near the Prox-Mine it will detonate.[7]


"We had this barely human Marine in our platoon who was righteous with the grenade launcher. He'd use it like a mortar; jamming the butt of his rifle in the ground and judging the angle by eye. He'd fire M40s into the upper jungle canopy and watch the airburst shred everything below. Legend had it he could detect the Beepops by smell and even figger the range from a single sniff..."
Beher, Jr. (from Aliens: Colonial Marines Technical Manual)

The U1 is the USCM's standard underbarrel attachment for the M41A and M41A MK2, although it could also be used with the M4RA. Marines could also replace the M41A MK2's standard U1 with the U7 Tac-Shotgun or the U4 Firebomb Launcher.

Loading and firing[]


A Marine demonstrating how to load and fire the U1 when attached to an M41A.

  1. Hand load the grenades into the four-round internal magazine.
  2. Use the pump action handle to prime the mechanism.
  3. Brace the weapon at the hip and squeeze the launcher's trigger. Although not the intended use, the parent weapon's stock can alternatively be placed on the ground and the U1 fired in a skyward arc, as a mortar.

Behind the Scenes[]

In Aliens, the underbarrel grenade launcher on the Pulse Rifle was built from a Remington Model 870 pump-action shotgun, cut down to fit under the rifle's barrel and covered with the foregrip and shroud of a Franchi SPAS-12.[11] In order for the Remington to fit under the weapon's main barrel, the shotgun's length had to be reduced to just 15 inches, and its shot capacity was limited to 3 rounds; Simon Atheron, the armorer from Bapty & Co. responsible for constructing the film's weapons, described mounting the shotguns on the Pulse Rifles as the most challenging thing he had to do for the film.[11]


  • The U1 Grenade Launcher's model in Aliens: Colonial Marines is reused for the U4 Firebomb Launcher and the Prox-Mine Launcher, as well as the H34 Fragmentation Round and 21S Arc Round launchers fitted to various Weyland-Yutani weapons in the game. Given that the Colonial Marines Technical Manual states the U1 is capable of using a variety of ammunition types, it seems possible these other underbarrel units are in fact intended to be a U1 loaded with different ammo, and that their in-game names are simply gameplay designations to denote this. The fact these visually similar launchers are named after ammunition they fire rather than having a specific designation (unlike the U1) further supports this theory.
  • The U1 Grenade Launcher is unlocked by default in Aliens: Colonial Marines for the M41A Pulse Rifle MK2 and at Marine Level 13 for the M4RA Battle Rifle.
  • The U1 had appeared numerous times before Aliens: Colonial Marines, but it wasn't until the game that the grenade launcher was given a designation.
  • The Weyland Storm Rifle appears to incorporate some type of underbarrel weapon which looks (intentionally) similar to the U1, most likely a grenade launcher or a shotgun.
  • Firing the grenade launcher in the 1999 Aliens versus Predator or Aliens versus Predator 2 acts as a mini-rocket launcher; the grenade launched from the launcher is not affected by arc trajectory.
  • Unlike every other Armat-manufactured underbarrel attachment in Aliens: Colonial Marines, the Prox-Mine Launcher does not have a "U-" designation as part of its name (e.g. U4 Firebomb Launcher). It is not clear if this is intentional or an oversight on the part of the developers.
  • The Prox-Mine Launcher in Aliens: Colonial Marines is visually identical to the U1 Grenade Launcher unit fitted to Pulse Rifles as standard. Given that the Colonial Marines Technical Manual states the U1 is capable of using a variety of ammunition types, it seems possible the name "Prox-Mine Launcher" is simply a gameplay designation, and that the weapon is in fact a U1 loaded with a different ammo type. The fact the Prox-Mine Launcher is named after ammunition it fires rather than having a specific designation (unlike the U1) further supports this theory.