Winchester SPIW
Winchester Repeating Arms Company · Assault Rifle · Prototype · 1964
Also known as: Winchester 1964 SPIW, Winchester-Olin SPIW, Olin SPIW, Special Purpose Individual Weapon
Overview
The Winchester SPIW is an experimental American flechette-firing assault rifle that Winchester (Olin) submitted to the U.S. Army's Special Purpose Individual Weapon (SPIW) program for the mid-1964 trials. It fired the saboted 5.6x44mm XM144 flechette round, a fin-stabilized dart leaving the 20-inch non-chromed smoothbore barrel at roughly 1,400 m/s, fed from a 60-round drum magazine at about 700 rounds per minute in both burst and full-auto. The gas-operated mechanism used a differential- or 'soft-recoil' scheme in which the barrel and receiver were allowed to recoil within a polymer housing/stock to tame burst dispersion, and the weapon was paired with a muzzle-mounted blow-forward grenade launcher firing three rounds in semi-automatic. It proved the weakest of the SPIW field, suffering from poor balance, handling, and reliability, and Winchester withdrew from the program after the 1964 trials.
Specifications
| Weight (empty) | 5200 g (183.4 oz) |
| Weight (loaded) | 5670 g (200.0 oz) |
| Overall Length | 940 mm (37.01") |
| Barrel Length | 508 mm (20.00") |
| Action Type | Gas Operated |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Magazine Capacity | 60 rounds |
| Magazine Type | Drum |
| Muzzle Velocity | 1398 m/s (4587 fps) |
| Muzzle Energy | 654 J (482 ft·lbf) |
| Effective Range | 400 m (437 yd) |
| Rate of Fire | 700 rpm |
| Barrel Rifling | Smoothbore |
| Frame Material | Steel |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Parkerized |
Calibers
- 5.6mm Flechette · primary — also known as XM144, 5.6x44mm XM144, 5.6mm SPIW flechette
Features
- Firing modes: Semi Automatic, Burst 3, Full Automatic
- Feed systems: Drum Magazine
- Safety mechanisms: Manual Safety
- Features: Flechette Ammunition, Smoothbore Barrel, Sabot Cartridge, Blow Forward Grenade Launcher, Integral Grenade Launcher, High Cyclic Rate, Drum Magazine
Service history
Operators
- United States Army
Production
Production years: 1964-1966
Only experimental prototypes built for the SPIW trials; never entered series production
Origin
Country of origin: United States
Designer: Winchester / Olin (Winchester-Western Division)
Discontinued: 1966
Notes
Winchester's entry competed against the AAI and Springfield Armory submissions (H&R also responded to the tender). It fired the same XM144 flechette cartridge as the Springfield gun. The soft-recoil concept never delivered as hoped: engineers found that at the weapon's modest ~700 rpm a recoil housing many times longer than the one fitted would have been needed to stop the receiver bottoming during a burst, so the accuracy benefit was lost. The flechette's sabot had to grip the dart tightly enough to drive it down the bore yet release cleanly at the muzzle, and the small darts could be deflected in flight by heavy rain. The one component judged worth keeping was Winchester's three-shot blow-forward grenade launcher, which Springfield's team continued to refine.
Background
The SPIW program reflected the U.S. Army's 1960s conviction that flechette salvos would outperform conventional bullets by raising hit probability. Winchester's contribution was judged one of the weakest of the field; testers found its handling poor, its soft-recoil mechanism impractical at the achievable cyclic rate, and its mechanism unreliable. The flechettes themselves were extremely expensive to produce and could be deflected even by heavy rain. The surviving prototype is held by the Rock Island Arsenal Museum.