M231 Firing Port Weapon
Colt's Manufacturing · Personal Defense Weapon · In Service · 1980
Also known as: M231 FPW, Port Firing Weapon
Overview
The M231 Firing Port Weapon (FPW) is a highly modified, automatic-only derivative of the Colt M16A1 developed by Rock Island Arsenal and produced by Colt for use from the firing ports of the M2/M3 Bradley Fighting Vehicle. Introduced in 1980, it uses a unique open-bolt fire-control group and a very high cyclic rate of around 1,225 rounds per minute. The base weapon has no iron sights and a telescoping steel-wire stock, and a threaded forend lets the barrel pass through a Bradley firing port while remaining removable for dismounted use.
Specifications
| Weight (empty) | 3329 g (117.4 oz) |
| Weight (loaded) | 3783 g (133.4 oz) |
| Overall Length | 717 mm (28.23") |
| Barrel Length | 396 mm (15.59") |
| Action Type | Gas Operated Long Stroke |
| Firing Mechanism | Open Bolt |
| Trigger Type | Single Stage |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 930 m/s (3051 fps) |
| Muzzle Energy | 1730 J (1276 ft·lbf) |
| Effective Range | 300 m (328 yd) |
| Rate of Fire | 1225 rpm |
| Barrel Rifling | Right Hand |
| Rifling Twist | 305 mm (12.01") |
| Number of Grooves | 6 |
| Frame Material | Aluminum |
| Barrel Material | Steel |
| Stock Material | Steel |
| Finish | Phosphate |
Calibers
- 5.56x45mm NATO · primary · 5.56mm NATO — also known as 5.56 NATO, 5.56x45mm, .223 Remington (parent), SS109
Features
- Firing modes: Full Automatic
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Manual Safety
- Features: Open Bolt Full Auto Only, No Iron Sights, Threaded Forend For Firing Port, Telescoping Wire Stock, High Cyclic Rate, Based On M16a1
Service history
Operators
- United States Army · adopted 1980 · as M231 FPW
Conflicts
- Gulf War (1990-1991)
- Iraq War (2003-2011)
Production
Production years: 1980-1985
Produced by Colt for Bradley Fighting Vehicle crews; exact figures not published
Origin
Country of origin: United States
Designer: Rock Island Arsenal
Notes
Open-bolt operation and the absence of conventional sights make the M231 a suppressive firing-port weapon rather than an aimed individual arm. When dismounted, crews could fit the wire stock and fire it from the shoulder. It saw service in the Gulf War and Iraq War and remains in inventory.
Background
Firing roughly 1,225 rounds per minute and lacking any sights, the M231 was never meant to be aimed; Bradley crews used it to hose the ground around their vehicle, and surplus examples are prized today as one of the rare open-bolt members of the M16 family.