This page covers the firearms in common use by U.S. Military forces, but does not include things like heavy or non-conventional weapons [bazookas, flamethrowers].
Rifle, Caliber 7.62mm, M14A3EditThe M14A3 is a full-caliber, selective-fire battle rifle with single-shot, 3-round-burst and automatic fire capabilities. It is the standard infantry service rifle for the U.S. military, chambers the 7.62x51mm American cartridge and is a replacement for the M1 series semi-automatic rifles [M1 Garand & M1 Carbine]. The bullet itself is very similar to the .30-06 Springfield round used by the M14's predecessor weapons, but is shorter - offering similar ballistic performance thanks to modern improvements in propellants while improving cycling rate and reducing the weight of firearms chambered for it. The M14 is a very reliable, powerful rifle - developing some 3,350 Joules / 2,470 foot-pounds of muzzle energy - and is also quite accurate for a standard service firearm. It is, however, heavier and bulkier than its principle competitors, the Russian SVT-50 rifle and SKS carbine. Despite having the capability, the M14 is very difficult to control from a standing position in automatic fire. The M14A3 model comes standard with an easily-detachable, lightweight folding bipod that clamps onto the front sling swivel, allowing soldiers to effectively use automatic fire from cover and from prone positions. In all other situations, semi-automatic fire is preferable, with bursts primarily used at short ranges. The -A3 version is also issued with new 25-round box magazines as a compromise between the 20- and 30-round clips issued for previous models, although it is fully compatible with these as well, and its vertical receiver mechanism allows it to be reloaded using the 8-round en bloc clips from the M1 Garand.
Pistol, Caliber 11.5mm, Automatic, Colt M1911A1EditThe United States Pistol, Caliber 11.5mm, Automatic, M1911A1 is the U.S. Military's principle service pistol. It is chambered for the 11.5mm ACP cartridge - which is actually 11.43x23mm and was originally known as the 0.45 ACP round prior to the U.S. conversion to the Metric System. As such, it is still generally called the "Colt .45" or simply "M1911" in common parlance. This high-caliber, heavy handgun has been America's go-to military pistol for more than fifty years and has proven itself in all manner of conflicts, generally outperforming (in terms of firepower at least) the smaller-caliber handguns used by most other nations. It is, however, predictably, heavier and harder to use accurately than most of its competitors.
Automatic Rifle, Caliber 7.62mm, M25A1EditThe United States Automatic Rifle, Caliber 7.62mm, M25A1 is effectively a replacement for the Browning Automatic Rifle / BAR and various older .30-caliber machine guns in U.S. service, such as the M1917 and M1919. It chambers the same new 7.62x51mm cartridge as the M14 Battle Rifle. Despite its designation, it is essentially a lightweight machine gun in the form of a rifle and is used more as such. It has a vertical feed mechanism and fires through an open bolt. Ammunition belts run down into the chamber through a top breech mechanism similar to the M1 Garand, either via long machine gun style ribbons of several thousand rounds held by a second soldier or through a shorter belt spooled up in an integral casket magazine on the underside, directly below the gun's receiver. This large, box-shaped hopper is removable but is part of how the weapon balances on the ground and so is almost always left attached. The M25 has a very high rate of fire - 1,100 to 1,300 rounds-per-minute - thanks to its un-delayed, open-bolt recoil operating cycle and, due to its construction, weighs only about as much as an M14. It can be fired from the hip as the operator advances, using the casket magazine, or from a braced position using long belts carried by an assistant in the manner of a machine gun. The loader also carried a detachable tripod mount for the weapon, although it more typically just uses the magazine and an integral bipod to provide stability in a prone or covered position.
Submachine Gun, Caliber 11.5mm, Thompson M1959EditThis modern iteration of the Thompson Submachine Gun is a weapon issued to American infantry NCOs, Officers and various Specialists - most famously being the standard firearm of U.S. Grenadiers. This Thompson is mechanically more complex than older models, more similar to the original M1921 and '28 versions. It has a very very high rate of fire, about 1500 rounds per minute, a slightly longer barrel and a number of minor changes to save on weight. The M1959 model is also unique for having a fire selector switch, which allows the operator to toggle on and off a bolt retarding mechanism that reduces the rate of fire down to about 700-800 rpm. It also has a 3-round burst setting. The standard Thompson M1959 uses a longer 40-round box magazine to compensate for the heightened rate of fire.
Rifle, Caliber 9mm, M17A4EditThe United States Rifle, Caliber 9mm, M17A4 is a high-powered precision semi-automatic rifle intended for use by snipers and squad marksmen. It was developed to replace the M1903 Springfield Bolt Action rifle, which had never been completely phased out due to the inability of the M1 Garand and M14 to easily accept a sniper scope. The M17 fires a unique, large diameter 9x64mm cartridge developed from various types of commercial big game hunt and sporting rifles. The casing is perportionally longer than is the norm, giving the bullet a stronger propellant load and thus greater muzzle velocity, while its modestly increased diameter means it retains lethality over longer distances. The round is, however - as one would expect - very powerful and imparts substantial recoil. Original prototypes of the M17 were capable of fully automatic and 3-round-burst fire, but this was judged to be a superfluous source of mechanical complexity and weight. The rifle's role as a high-powered precision weapon and the large diameter of its cartridge, which results in a small 10-round magazine, makes anything other than semi-automatic fire essentially useless. (Note that the M17 shown here is loaded with a non-standard 20-round sickle magazine).
Carbine, Caliber 9mm, M19A3Edit
The M19A3 Carbine is a shortened version of the M17 precision rifle and a replacement of the M1 Carbine. It is used by specialist troops such as engineers, radio-operators and vehicle crewmen, as well as by paratroopers - soldiers whose roles are unsuited to the size and weight of a standard M14 Battle Rifle. Like the M17, the M19 is capable only of semi-automatic fire. This is not considered a substantial handicap, however, because the full-auto feature of the M14 and other selective-fire battle rifles is rarely used. The M17 is also superior in power and accuracy to the M14, and due to the heavy charge of its round has about the same effective range despite a much shorter barrel. Its biggest disadvantage is its substantial recoil.