Prior to the wide scale adoption of man-portable, shoulder-fired rocket weapons during the Cold War, the "rifle grenade" was used to expand the battlefield capabilities of the basic infantryman during World War 2 (1939-1945). It now allowed the rifleman to launch, through indirect and direct fire, standard hand grenades at range - useful in engaging dug-in enemy. The standardized rifle grenade deployed by American forces in the early-to-middle years of the war became the "M17"and this weapon was nothing more than a special adapter - making up the rifle grenade's body - fitted to the common Mk 2 "Pineapple" anti-personnel fragmentation grenade. The weapon was fitted over the barrel of the service rifle and actuated through use of a blank .30-06 rifle cartridge. The M17 entered service in 1941 and was in standardized, frontline use into 1944 by which time the series was officially succeeded by the "M1 Projection Adaptor" which appeared from 1943 onwards - this new product retained the Mk 2 hand grenade as its warhead.
The M17 carried a base 22 gram TNT filling and was detonated through an impact fuse integrated to the base. With the Mk 2 grenade screwed onto the launcher unit, the completed system measured 248mm long and held a weight of 667 grams with a diameter reaching 57mm. Unlike traditional hand grenades, which generally exposed the infantryman to enemy fire while throwing, rifle grenades allowed for indirect, angled fire which protected the operator some from battlefield dangers. Additionally, engagement ranges were improved. Despite the benefits, there did prove some limitations to the effectiveness of rifle grenades - the M17, in particular, required hardened surfaces to properly detonate which sometimes left ordnance unexploded when landing on softer terrains. The weapon also increased the length of an already long, and heavy, service rifle when fitted to the muzzle. The detonating power and fragmentation of the grenade was also unchanged from its thrown form - so blast radius remained equal to that seen in the original design.
Nevertheless, there proved a need for such weapons and the M17 gave years of faithful service. It could prove the difference between an infantry squad being pinned down for hours in the mud under machine gun fire or an infantry squad being able to engage the unsuspecting machine gun crew with a foxhole-clearing device.