M950P loaded with a 30-round magazine. Note the larger, slightly longer 5x scope, integral foregrip, and the switch on top of the handguard for opening and closing the vent holes.

The M950P is a heavy-barrel assault rifle developed from and as a compliment to the M16A5P. This was done as part of the switch to an M16-based common weapon platform which could be used for a standard-issue rifle as well as a marksman rifle and squad automatic weapon.

The M950P is used as the United States military’s primary squad automatic weapon, with three per infantry squad. Heavier machine guns like the M45 and M56 Smartguns are deployed in Special Forces units and the heavy weapons platoon of each infantry company, not in regular infantry squads.

Weapon Designation:Rifle, 6.2mm, Pulse-Fired, M950P
Type:Heavy-Barrel Assault Rifle
Place of Origin:United States
In Service:2031-present
Production History:
Manufacturer:Colt Arms Manufacturing
Weight:7.6 lb (3.35 kg)
Length:39.5 in (1,003 mm) (full stock with buttplate extended/collapsible stock extended)
38.5 in (978 mm) (full stock with buttplate retracted)
35.5 in (901 mm) (collapsible stock retracted)
Barrel Length:20 in (508 mm)
Action:Gas-operated direct impingement, electronically ignited cartridges
Rate of Fire:700 rounds/min cyclic
Muzzle Velocity:3,976 ft/s (1,212 m/s) with M658 round
Muzzle Energy:2,036 ft/lbs (2,761 Joules) with M658 round
Effective Range:800 m (875 yd)
Feed System:100-round detachable saddle drum magazine
Sights:Colt 5x scope, backup iron sights


Immediately after the M16A5P was accepted as the United States military’s standard rifle, work began on a heavy-barrel version for use as a squad automatic weapon. The M950P was designed, tested, and accepted within one year, its development running both parallel and simultaneously to the M656P, a marksman version of the M16A5P.


The M950P is a modified M16A5P, with three key differences: a slightly larger Colt-built scope with 5x magnification, a heavier barrel, and a new handguard with a built-in vertical foregrip. Although it is capable of using the M16A5P’s 30-round box magazines, it is intended for use with 100-round saddle drum magazines.


The barrel is identical to the M16A5P’s barrel except for the thicker 0.8 inch diameter behind the front sight post. The thicker profile gives the barrel more mass and better heat dispersion, making the rifle more suited for sustained automatic fire.


The M950P uses a Colt 5x25mm scope, which is simply a slightly larger, higher-magnification version of the 3.5x20mm scope. Although it does not significantly increase the range at which the weapon can be used, as 800 meters is approximately the limit of the M658 cartridge, it does make engaging targets within 800 meters noticeably easier than the 3.5x scope.


The M950P is equipped with a highly unusual handguard design. Although it appears to be a standard A2-style handguard with an integrated vertical foregrip, it has a very unique feature: it can be entirely sealed to allow it to be filled with water for more effective cooling.

 To accommodate this, the bottom half of the guard has no vent holes, and the vent holes on the top half of the guard can either be left open or closed by a single piece of polymer that rides in a pair of slots just under the vent holes, with corresponding holes drilled in it. To close the vent holes, a small switch towards the front end of the handguard is pushed to the left out of its locking notch, pushed forward to slide the polymer shield over the holes, and then pushed to the right into the forward locking notch to lock the shield in the closed position. The joints between the two halves as well as the ends are completely sealed off with rubber gaskets.

The water-cooling feature is not necessary for proper functioning of the weapon, and it can be used in air-cooled mode as long as the vent holes are left open. If water-cooling is desired, the handguard must merely be filled with water and the vent holes closed. Operators are advised to fill the handguard until it overflows to make sure that there is no air space and no possibility of the water inside making undesired sloshing sounds while moving. Although it is intended for use with water, some troops have been known to use automotive coolant instead, which works even more effectively.

Although it is possible for one of the seals to separate slightly under extremely rough handling and allow some or all of the cooling fluid to leak out, the worst that will happen is the loss of the fluid. No damage to the rifle’s functionality will occur and most often, the problem can be fixed by simply disassembling and reassembling the handguard to reform the seal.

Additional Accessories

The M950P is capable of using all of the accessories meant for the M16A5P and is issued with a M3A1 clamp-on bipod. This simple bipod is a lightened, strengthened version of the M3 bipod used in the Vietnam War and is mounted by squeezing the legs together and opening the jaws until they slip over the barrel. When not in use, the bipod is stored in a pouch which holds it in the closed position. The M3A1 is also used on the M656P marksman rifle.

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