AAI ACR
AAI Corporation · Assault Rifle · Prototype · 1989
Also known as: AAI Advanced Combat Rifle, Aircraft Armaments ACR
Overview
The AAI ACR is a prototype flechette-firing assault rifle developed by the AAI Corporation for the United States Army's Advanced Combat Rifle (ACR) program of 1989-1990. Building on the company's earlier SPIW and XM19 serial-flechette work, it fired a saboted 1.6mm fin-stabilized steel flechette packaged in a 5.56x45mm brass case at roughly 1,400 m/s, giving an extremely flat trajectory and very low recoil impulse. A gas-operated three-chamber breech allowed a high-cyclic three-round burst, while a proprietary magazine and altered magazine well prevented the accidental loading of standard 5.56mm NATO ammunition. Like the other ACR entrants, it failed to demonstrate the required 100 percent hit-probability improvement over the M16A2 and was not adopted.
Specifications
| Weight (empty) | 3530 g (124.5 oz) |
| Weight (loaded) | 4260 g (150.3 oz) |
| Overall Length | 1016 mm (40.00") |
| Barrel Length | 508 mm (20.00") |
| Action Type | Gas Operated |
| Firing Mechanism | Hammer Fired |
| Trigger Type | Single Stage |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 1402 m/s (4600 fps) |
| Muzzle Energy | 649 J (479 ft·lbf) |
| Effective Range | 610 m (667 yd) |
| Rate of Fire | 1800 rpm |
| Barrel Rifling | Right Hand |
| Rifling Twist | 2159 mm (85.00") |
| Frame Material | Steel |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Phosphate |
Calibers
- 5.56mm Flechette · primary — also known as 5.56x45mm Flechette, AAI ACR Flechette, Saboted Light Armor Penetrator Flechette
Features
- Firing modes: Semi Automatic, Burst 3
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Manual Safety
- Features: Three Chamber Breech, Saboted Flechette Ammunition, Proprietary Magazine Well, Detachable 4x Optic, Iron Sights, Low Recoil Impulse
Service history
Operators
- United States Army
Production
Production years: 1989-1990
Small number of prototypes built for the ACR program trials; never mass produced
Origin
Country of origin: United States
Designer: AAI Corporation
Discontinued: 1990
Notes
Cyclic rate within the three-round burst was approximately 1,800 rpm; sustained semi-automatic fire was also possible. The flechette weighed about 0.66 g, with the full sabot-and-flechette assembly around 1.36 g.
Background
The AAI ACR was the culmination of decades of US flechette-rifle research that began with the Special Purpose Individual Weapon (SPIW) program and the XM19 serial flechette rifle. Its dart-like projectile flew so fast and flat that AAI's entry was praised for flechette reliability, yet the whole ACR program ended without a winner because no design could beat the M16A2 by the required margin.