One of the more storied experimental weapons that was developed for the U.S. military but never adopted by the Defense Department is the EX-41 grenade launcher.
The EX-41 grenade launcher was developed during the 1990s – mostly at the Naval Ordnance Station in Louisville, Kentucky. The plan was to develop a pump action, multi-shot grenade launcher for the U.S. Marine Corps. The U.S. Defense Department had hoped that the EX-41 could be used to replace the single-shot M203 grenade launcher. The EX-41 was officially developed under the "Army’s Bursting Munitions Technology" program. The weapon was also known as the "Shoulder Fired-Weapon" (SFW).
The design of the EX-41 grenade launcher called for the weapon to weigh about 6.5 kilograms and have a firing range of 3,000 meters. Developers hoped to create a hybrid grenade launcher that combined the best of both low velocity and high velocity grenade launchers that had been developed previously. The EX-41 was to fire 40 millimeter grenades and carry four grenades at a time in a tube magazine.
However, the EX-41 grenade launcher never progressed beyond the development of a single prototype and the program was abandoned in the late 1990s. In the end, developers concluded it would take too long to perfect the hybrid design of a low velocity and high velocity grenade launcher than they had envisioned. Instead, the U.S. Defense Department moved forward with other grenade launchers that were easier to develop such as the M32 and M79.