A prototype Shoulder-Launched Multipurpose Assault Weapon (SMAW) which fires nerf rounds is tested in this video. No mention of who is behind this project but it seems a DIY project not meant for commercial production (unless we're mistaken). We cannot make out the propellant used with it, but the SMAW surely has a long range. The real SMAW is in use in the US Military since 1984 and is based on Israel's B-300.

Hat tip to Rambo Gone Amok for the link.