M231 FPW
Country of origin

United States


Rock Island Arsenal

Year(s) designed


Production began


Weapon type

Firing Port Weapon/Assault rifle


5.56x45mm NATO


Gas-operated, rotating bolt

Overall length

28.25 in. (71.76 cm)

Barrel length

396 mm (15.6 in)

Weight empty

Empty - 7.34 lb (3.33 kg) w/ 30 round magazine - 8.34 lb (3.79 kg)

Magazine/Cylinder capacity

30-round STANAG Magazine

Cyclic rate

Sustained (Short Bursts) - 50 to 60 rds per min Minimum Cyclic - 1225 rds per min

Maximum effective range

328 yds (300 m)

Used by

United States of America

The M231 Firing Port Weapon (FPW) is an adapted version of the M16 assault rifle for firing from ports on the M2/M3 Bradley AFV. The infantry's normal M16s are too long for use in a "buttoned up" APC, so the FPW was developed to provide a suitable weapon for this role. Designed by the Rock Island Arsenal, the M231 FPW remains in service, although all but the rear two firing ports on the Bradley have been removed.


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