Aliens is the 1986 sequel to Alien, directed by James Cameron. Sigourney Weaver returns as Ripley, who travels with a platoon of US Colonial Marines to investigate a loss of contact with the colony established on the same planet discovered by the crew of the Nostromo. Unlike the original film, the majority of the weapons seen in the sequel were actual firearms visually modified for the production.
The following weapons were used in the film Aliens:
M41A Pulse Rifle
The Marines of the USCMC (United States Colonial Marine Corps) famously carry the M41A Pulse Rifle as their standard issue weapon. In the film, the weapon is described as a futuristic assault rifle with a magazine capacity of 99 rounds of 10x24mm caseless armor-piercing ammunition with a pump action 30mm grenade launcher mounted underneath the barrel. The pulse rifle was constructed from an M1A1 Thompson submachine gun fitted with a cutdown Remington 870 shotgun underneath with the heat shield and foregrip of a SPAS 12 covering it. At the end of the film, Ripley (Sigourney Weaver) fastens one of these rifles to an M240 Flamethrower in her attempt to rescue Newt (Carrie Henn).
M56 Smart Gun
Both PFC J. Vasquez (Jenette Goldstein), and Private M. Drake (Mark Rolston) use M56 Smart Guns. These were made from German MG42 machine guns. The body-mounting apparatus was made from Steadicam "arms", with other miscellaneous parts coming from various motorcycles, most notably the handlebars used for the weapon's grips.
Another weapon used by the Marines is the M240 Flamethrower, most notably used by Gunnery Sergeant A. Apone (Al Matthews), Private M. Drake (Mark Rolston), and Ripley (Sigourney Weaver) when she famously tapes it to an M41A Pulse Rifle before she goes to rescue Newt (Carrie Henn). These flamethrowers also appear to have been created from parts from M16 rifles with the M203 handguard. The 'faux' flamethrower used the upper receiver assembly of an M16A1 - cut into two parts, using the top handle facing forward, but the section with the ejection port turned backwards.
Aliens is notable as being one of few films to employ military-spec liquid-fuelled flamethrowers in its production, as opposed to the vastly more common (and far safer) gas-powered models usually seen in films (although some gas-burning models are also used in the movie, usually in scenes with actual actors using the weapons). The liquid fuel flamethrower is most notably seen in the sequence where Ripley incinerates the Alien nest.
Ithaca 37 "Stakeout"
Corporal Hicks' (Michael Biehn) shotgun is an Ithaca 37 "Stakeout" which he keeps for "Close Encounters". In one memorable scene, Hicks sticks the barrel of the weapon in an Alien's mouth, and yells "Eat this!" before blowing its head off.
Heckler & Koch VP70
The Heckler & Koch VP70 is the service pistol of the Marines in the movie. This gun is notably seen in the hands of Private Frost (Ricco Ross) just before the Aliens attack. Cpl. Ferro (Colette Hiller) attempts to draw hers from its holster, but is unable to in time when an Alien gets aboard her ship. Lieutenant Gorman (William Hope) uses one to shoot at Aliens during the airshaft scene. Another VP70 is seen given by Vasquez to the synthetic droid Bishop (Lance Henriksen), who then declines to take it and passes it back to Ripley (Sigourney Weaver).
In the special features included with the Collector's Edition DVD, it is mentioned by one of the film's armorers that the VP-70 was chosen as the standard issue sidearm for the Colonial Marines because of its "futuristic look" as well as its relative obscurity.
UA571-C Remote Automated Sentry System
In the extended version of the film, the Marines set up sentry turrets in the hallways leading to their refuge. These were built upon WWII German MG42 machine guns, the same used for the smartguns and provided by Bapty's (movie armorer of the UK). Only the ammo drums on the side are from WW1 German Spandau Maxim LMG 08/15 machine guns
Smith & Wesson Model 39
PFC Vasquez (Jenette Goldstein) uses a blued Smith & Wesson Model 39 with Ivory grips as her sidearm. She most notably uses it to kill an Alien while moving through the vents, but burns her foot from the creature's acidic blood in the process.
The pistol was referred to as the M4A3 in the ALIENS: Colonial Marines Technical Manual by Lee Brimmicombe-Wood. It was supposed to be a 10mm cased-ammo pistol with a 12-round magazine that had been recently replaced in service by the VP-70.
The Cheyenne dropship, a fictional VTOL aircraft in the Aliens universe, can be seen with a multi-barrelled, chin-mounted cannon of some kind. Some of the barrels appear to be chambered for different calibres of ammunition, and the weapon likely operates in a rotary fashion similar to a minigun (owing to the circular arrangement of the barrels). However, it is never used in the film.
Seen on the gun racks in the USS Sulaco's armory.
Several L85A1 rifles are seen on the gun racks in the Sulaco's armory.
Seen on the gun racks in the USS Sulaco's armory.