YouTube channel Parabellum Arms shows of this amazing home-made rubber band gun modeled after the M41A Pulse Rifle wielded by the Colonial Marines of the Alien franchise. The gun was developed over two different iterations, which feature an underslung pump-action rubber band launcher (w/ faux shell ejection), and a main rubber band launcher that can feed from detachable magazines, and is capable of both semi and automatic fire (with a rate of fire of 900 rounds per minute). The M41A also features ambi sling mounts, and a telescoping stock.
You can check out more of Parabellum Arms’ creations on his YouTube channel, and buy plans of the guns via his Etsy shop.