The M41A Pulse Rifle is the standard issue weapon of the United States Colonial Marine Corps within the Alien universe. It also appears on the list of available weapons on the HUD of the T-X. By virtue of crossover appearances in Aliens vs. Predator vs. The Terminator, it is listed here for completeness.
The M41A Pulse Rifle fires 10mm caseless, armor piercing, high-explosive ammunition and includes a "pump-shotgun" style 30mm grenade launcher in an over-under configuration.
The M41A Pulse Rifle is a fictional weapon used in various sci-fi franchises (most notably, the Alien franchise). The prop used in Aliens and later movies is a hybrid of several actual firearms (Thompson SMG, SPAS-12, Remington 870) finished with a futuristic aluminium shell.
There are no specific technical details for the Pulse Rifle, as it is a completely fictitious and generic weapon used in many movies, comic books, etc. Its appearances include movies, video games, and franchises that were created, or co-written by James Cameron (Aliens, T2), Dan O'Bannon (Alien, Heavy Metal), Todd McFarlane (Spider Man), John Romero (Quake), and George Lucas (THX-1138). Any technical details found about the weapon are most likely related to the Alien franchise, as its other appearances are merely incidental and used as a basic-stock futuristic weapon; not important enough to the franchise to detail.