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Special Purpose Individual Weapon
The Special Purpose Individual Weapon (SPIW) was a long-running United States Army program to develop, in part, a flechette-firing "rifle", though other concepts were also involved. The concepts continued to be tested under the Future Rifle Program and again in the 1980s under the Advanced Combat Rifle program, but neither program resulted in a system useful enough to warrant replacing the M16.
The idea of a flechette-firing individual weapon started in earnest during the Army's Project SALVO. SALVO had earlier concluded that a small weapon with a high rate of fire would be considerably deadlier than the large "full power" weapons being developed in the 1950s, and followed several lines of investigation to find the best way to provide high firing rates. SALVO had a small number of "duplex load" weapons developed, where two bullets were stacked, while Springfield Armory and Olin/Winchester both entered multiple barrel firearms.
Even before the SALVO tests, Irwin Barr of AAI Corporation had been developing single and multiple flechette cartridges. The Navy became sufficiently interested in the concept to provide him with some development funding from the Office of Naval Research, resulting in a 12 gauge shotgun shell firing 32 flechettes. The Army later added funding as well, and AAI was invited to SALVO. In SALVO testing they were found to be able to penetrate one side of a standard steel helmet at 500 yards (460 m)—excellent given their light weight—but the dispersion of the darts was so great as to make them only marginally useful.
Further development continued by adapting a Winchester Model 70 rifle with new XM110 5.6x53mm rounds firing a single dart. The result was a weapon with somewhat less accuracy than the .308Win (7.62×51mm NATO) rounds, but with equal penetration and a trajectory so flat it could be fired with no sight adjustment out to 400 yards (370 m). Better yet the rounds were very light, and had almost no recoil in comparison to even the .22-caliber weapons under development. This meant they could be fired at extremely high rates of fire, from a very lightweight weapon.
Project SALVO began in 1951 and was based on the assumption that firing multiple projectiles would increase the probability of hitting the target. Consideration to lighter ammunition types and rifle/grenade launcher combinations was 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 3.5 pounds (1.6 kilograms), fully loaded with 60 rounds. Accordingly, the Army became extremely interested in the weapon.[citation needed] The conclusion of Project SALVO was to adopt the Armalite AR-15, which became the M16 rifle.
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 10 pounds (4.5 kilograms) 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 (or sized in 0.22 by 2.09 inches, while Springfield and Winchester used a new 5.6×44mm (0.22 by 1.73 inches) XM144 cartridge. The H&R design loaded the dart from the XM144 into their own cartridge design.
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Special Purpose Individual Weapon
The Special Purpose Individual Weapon (SPIW) was a long-running United States Army program to develop, in part, a flechette-firing "rifle", though other concepts were also involved. The concepts continued to be tested under the Future Rifle Program and again in the 1980s under the Advanced Combat Rifle program, but neither program resulted in a system useful enough to warrant replacing the M16.
The idea of a flechette-firing individual weapon started in earnest during the Army's Project SALVO. SALVO had earlier concluded that a small weapon with a high rate of fire would be considerably deadlier than the large "full power" weapons being developed in the 1950s, and followed several lines of investigation to find the best way to provide high firing rates. SALVO had a small number of "duplex load" weapons developed, where two bullets were stacked, while Springfield Armory and Olin/Winchester both entered multiple barrel firearms.
Even before the SALVO tests, Irwin Barr of AAI Corporation had been developing single and multiple flechette cartridges. The Navy became sufficiently interested in the concept to provide him with some development funding from the Office of Naval Research, resulting in a 12 gauge shotgun shell firing 32 flechettes. The Army later added funding as well, and AAI was invited to SALVO. In SALVO testing they were found to be able to penetrate one side of a standard steel helmet at 500 yards (460 m)—excellent given their light weight—but the dispersion of the darts was so great as to make them only marginally useful.
Further development continued by adapting a Winchester Model 70 rifle with new XM110 5.6x53mm rounds firing a single dart. The result was a weapon with somewhat less accuracy than the .308Win (7.62×51mm NATO) rounds, but with equal penetration and a trajectory so flat it could be fired with no sight adjustment out to 400 yards (370 m). Better yet the rounds were very light, and had almost no recoil in comparison to even the .22-caliber weapons under development. This meant they could be fired at extremely high rates of fire, from a very lightweight weapon.
Project SALVO began in 1951 and was based on the assumption that firing multiple projectiles would increase the probability of hitting the target. Consideration to lighter ammunition types and rifle/grenade launcher combinations was 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 3.5 pounds (1.6 kilograms), fully loaded with 60 rounds. Accordingly, the Army became extremely interested in the weapon.[citation needed] The conclusion of Project SALVO was to adopt the Armalite AR-15, which became the M16 rifle.
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 10 pounds (4.5 kilograms) 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 (or sized in 0.22 by 2.09 inches, while Springfield and Winchester used a new 5.6×44mm (0.22 by 1.73 inches) XM144 cartridge. The H&R design loaded the dart from the XM144 into their own cartridge design.