The M231 Firing Port Weapon is a rather obscure footnote in US Small Arms history. Thanks to Marty Bordson, owner of Badger Ordnance, I recently got the chance to fire one.
Designed to be shot from the firing ports of the M2 Bradley Fighting Vehicle (the M2 was the Infantry variant), the M231 was based on the M16A1. As you can see, it featured a short, threaded handguard which was screwed into place in the firing port. Initially, the M231 featured a wire stock, reminiscent of the M3 “Grease Gun” but it was later removed as it was prone to rattle off and become a nuisance in the vehicle. Although, the real reason was probably to dissuade the rifle’s use in place of the standard M16 by dismounted Infantry.
Below, you can see the modified selector lever, peculiar to the M231. It is either SAFE or AUTO and the SOP was to fire Tracer ammo, aimed through a vision block. The M231 was meant to deal with enemy dismounts who might try to engage from the sides and rear of the Bradley.
Marty made a couple of mods to the rifle in order to use it while hunting hogs. He changed out the flash hider so it would accept a Mack Brothers suppressor and fitted a mount and PEQ-15 to the carrying handle. Obviously, that didn’t do me any good during the day. I sighted over the top of the receiver and aimed at the berm.
Perhaps the most interesting feature of the M231 is that it fires from the open bolt to help keep it cool. With a cyclic rate of around 1200 rpm, the added suppressor just sped it up, and also exacerbated the gas issues. I also had access to a Magpul D60 PMAG, while those using the M231 in its heyday would have only had USGI 30 rd magazines. My firing hand was covered in carbon when the magazine was finished and I had to stop halfway through, due to the back gas. The video below shows me firing the second half of the magazine. I can only imagine what it was like in the vehicle when there were six firing at once. For a period, there was supposed to be a vent hose for the gas, but the few accounts I’ve heard of these actually being fired from within the vehicle, it didn’t work.
Eventually, the M2 Bradley was upgraded with slab sides designed to accept reactive armor panels which eliminated the side firing ports. However, the M231 is said to soldier on, at least in arms rooms, as the M2 has retained the two firing ports on the rear hatch. As late as the invasion of Iraq, armored troops were spotted using the M231.
Pictured – Radical Pistol 308WIN, 12.5”
