given. Flechettes were found to be inaccurate and expelled fiberglass fragments with each round fired. SALVO mainly studied weapons and ammunition as opposed to developing them. It determined that higher velocity projectiles, smaller than .308 (7.62 mm), had equal or greater lethality with less weight. It also found that fully automatic fire did not increase hit probability. Since the Army was by this time only interested in fully automatic weapons, Barr suggested that they build a multiple barrel prototype in order to quickly test the concept. Various multiple barrel rifles entered the project. The resulting "burst simulators" were tested in 1961, and the general conclusion was that the light weight of the flechette meant that it could be fired at extremely high rates of fire, the baseline being 2300 rpm, from a weapon of only , fully loaded with 60 rounds. Accordingly, the Army became extremely interested in the weapon. The conclusion of Project SALVO was to adopt the Armalite AR-15, which became the M16 rifle. Project NIBLICK Meanwhile, the Army's Operations Research Office, ORO, had been working on Project NIBLICK, follow-on to SALVO to develop a modern grenade launcher. Interested in the original shotgun-type shells, they recommended development of a dedicated flechette-firing weapon combined with a grenade launcher, the SPIW. The final requirements resulted in an over-under weapon, firing flechettes from one barrel, and grenades from the other. It was to weigh under fully loaded with three grenades and 60 flechettes. Four companies responded to the contract tender: AAI, Springfield Armory, Winchester Arms and Harrington & Richardson. AAI continued with the original 5.6×53mm XM110 rounds, while Springfield and Winchester used a new 5.6×44mm XM144 cartridge. The H&R design loaded the dart from the XM144 into their own cartridge design. The H&R design was the most advanced. It mounted the dart between three plastic sabots in a triangular plastic cartridge. When fired, the sabots were discarded early in small "sub-barrels" while the dart continued down the main barrel. Although the rounds were lightweight the weapon itself was not, at loaded, and the weapon was quickly eliminated from the contest. Winchester's design used a "soft recoil" stock which absorbed the recoil of an individual round in a spring. The idea was to allow three rounds to be fired before the spring was completely compressed, meaning that there was very little recoil until the end of the burst. This was intended to