An M4 with an aftermarket Government-type spur hammer fitted.

The M4 is a compact M1911-style pistol used by the US military as one of two standard-issue sidearms, the other being the H&K M86.

Weapon Designation:Pistol, 9mm, Semiautomatic, M4
Place of Origin:United States
In Service:2037-present
Production History:
Manufacturer:Rock Island Arsenal
Weight:1.625 lb (0.737 kg)
Length:7.5 in (190.5 mm)
Barrel Length:4 in (101.6 mm)
Cartridge:9x19mm Parabellum
Rate of Fire:Semiautomatic
Muzzle Velocity:1,550 ft/s (472 m/s) with M990D fluted round
Muzzle Energy:480 ft/lbs (651 Joules) with M990D fluted round
Effective Range:50 m (55 yd)
Feed System:10-round detachable box magazine
Sights:Iron sights


Several years after the Sig Sauer P320 MHS was accepted by the US military as the M17 pistol along with a compact variant, the M18, complaints began to surface from some users about the size of the M18 compact. Although it was intended to be lighter and easier to carry than the full-sized M17, certain users, like plainclothes agents in the Air Force Office of Special Investigations, Army Criminal Investigation Command, and Naval Criminal Investigative Service, as well as some aircrew members and other personnel in non-combat roles wanted a lighter, more compact handgun. Most specifically cited the large magazine capacity of the M18 as unnecessary for their role and the double-stack magazine and resultant grip size as making the gun too wide. After almost twenty years of these complaints, the military began a search for a similar compact, lightweight handgun with a single-stack magazine. Although several designs were submitted, including Sig Sauer’s P239, in the end the competition was won by Rock Island Arsenal’s P1911C9, largely because it performed just as well as all the competing handguns during trials but at a lower cost. With the adoption of a low-profile safety reminiscent of the traditional M1911 Government model safety instead of its factory-standard extended safety, the P1911C9 was adopted as the M4 pistol in 2037.

By the 2170s, the M4 was still serving as one of the military’s two primary sidearms, although this time alongside the M86, not the M58, and was actually more common than the M86. The reason for this was that changing regulations allowed regular infantry to carry sidearms if they so chose, and while many felt that extra weight was not worthwhile, other service members considered having a backup weapon as an excellent idea, and the smaller, lighter M4 was more popular than the M86 with most of these troops. However, it was still fairly common to see regular infantry carrying the M86, and most Special Forces personnel, especially Reconnaissance In Force Teams, preferred it to the M4.


Most of the features of the M4 can be determined from its factory name, P1911C9, where P stands for “polymer”, meaning the gun uses a polymer frame, 1911 for the pattern, C for “Compact”, as the gun has a four-inch barrel, and 9 for “9mm”, the caliber the gun is chambered in. The polymer frame makes the gun exceptionally light at only 26.3 ounces, and the short barrel and single-stack magazine make for a short, slim weapon compared to the M17 and M18. Although only ten rounds can be fit in the M4’s magazine compared to the M18’s seventeen, the lower capacity and narrower magazine were specifically requested as features for the new pistol, while a user who did want to carry more ammunition could actually carry as much or more ammunition than the M18; for example, a person carrying an M18 with a loaded magazine, a round in the chamber, and two spare magazines in pouches would have fifty-two rounds at their disposal. A person carrying an M4 with a loaded magazine, a round in the chamber, and four spare magazines in double pouches only a fraction of an inch thicker than a single pouch for an M18 magazine would have fifty-one rounds available in a more convenient pistol.

Most M4s were fitted with Commander-style round hammers and a Government-style low-profile grip safety, but some were retrofitted by their users with aftermarket Government-type spur hammers for greater ease of cocking. Although the P1911C9 featured an extended thumb safety, the M4 was fitted with a Government-model safety that was much less likely to snag on clothing or equipment when drawn. The M4 is also available with interchangeable grip panels to accommodate users with different hand sizes.

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