Springfield SPIW
Springfield Armory · Assault Rifle · Prototype · 1963
Also known as: Springfield Armory SPIW, Special Purpose Individual Weapon
Overview
The Springfield SPIW is an experimental American assault rifle developed by Springfield Armory for the U.S. Army's Special Purpose Individual Weapon program of the 1960s. It fired the 5.6x44mm XM144 flechette cartridge from a 60-round magazine at a cyclic rate of up to 1,700 rounds per minute, and carried an integral three-shot 40mm grenade launcher beneath the barrel. Built first as a bullpup and later in a conventional layout, the design never entered service: like the rival AAI, Winchester and Harrington & Richardson submissions, it was too heavy and unreliable, and the program was abandoned in favor of the M16.
Specifications
| Weight (empty) | 5000 g (176.4 oz) |
| Weight (loaded) | 6400 g (225.8 oz) |
| Overall Length | 965 mm (37.99") |
| Barrel Length | 660 mm (25.98") |
| Action Type | Gas Operated |
| Firing Mechanism | Hammer Fired |
| Magazine Capacity | 60 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 1402 m/s (4600 fps) |
| Muzzle Energy | 648 J (478 ft·lbf) |
| Effective Range | 500 m (547 yd) |
| Rate of Fire | 1700 rpm |
| Barrel Rifling | Smoothbore |
| Frame Material | Steel |
| Barrel Material | Steel |
| Finish | Parkerized |
Calibers
- 5.6mm Flechette · primary — also known as XM110, XM144, XM645, 5.6x44mm, 5.6mm SPIW flechette
Features
- Firing modes: Full Automatic, Burst 3
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Manual Safety
- Features: Integral Grenade Launcher, Flechette Ammunition, High Cyclic Rate Burst, 60 Round Magazine
Service history
Operators
- United States Army · as SPIW (experimental)
Production
Production years: 1963-1966
Only a small number of prototypes were built for SPIW program trials; never mass-produced
Origin
Country of origin: United States
Designer: Springfield Armory
Discontinued: 1966
Notes
The 1964 bullpup prototype, with its distinctive 60-round staggered box magazine loaded behind the pistol grip, is the best-known Springfield SPIW and is preserved at the U.S. Army Ordnance Museum. Later 1965-1966 revisions moved to a conventional layout, adopted the Winchester-style grenade launcher, and used the improved XM216 flechette round.
Background
The SPIW program sought a futuristic infantry weapon firing fin-stabilized flechette darts at extreme velocity, but every contender, including Springfield's, busted the 10-pound weight limit and the flechette ammunition proved finicky, leaving the conventional M16 to soldier on.