Automatic firearm

An automatic firearm is a self-loading weapon designed to fire rounds continuously. This happens when the trigger mechanism is actuated, or pressed. These firearms are significant because they can harvest excess energy from a previous discharge. This harvested energy feeds a new ammunition round into the chamber. Then, a hammer or striker delivers an impact to the primer. This impact ignites the propellant and discharges the projectile, which could be a bullet, shot, or slug.

There are distinct ways these weapons cycle through their functions. A fully automatic firearm cycles both the feeding and the ignition procedures automatically. It will fire continuously as long as the trigger remains depressed and ammunition is available from a magazine or a belt. In contrast, a semi-automatic firearm is only self-loading. It chambers new rounds automatically, but it does not fire them automatically. The user must manually release and re-actuate the trigger to fire each individual shot. A burst-fire firearm sits between these two types. It fires a brief, continuous burst of multiple rounds with each trigger pull. After the burst, the user must reset the trigger to fire again.

Automatic firearms are categorized into several specific types based on their design and use. Automatic rifles are common in modern militaries and often feature selective fire. Assault rifles are a specific type of rifle that use an intermediate cartridge and a high-capacity detachable magazine. Battle rifles are similar but use a full-powered cartridge. Machine guns are heavier weapons used for suppressive fire. They are often attached to a mount or supported by a bipod and frequently use belt-fed ammunition.

Other specialized categories include submachine guns and personal defense weapons. Submachine guns are short rifles that typically use pistol cartridges. Personal defense weapons are a newer breed of firearm. They combine the light weight of a submachine gun with the medium power of a rifle cartridge. This allows them to have body armor penetration capabilities. There are also machine pistols, which are handgun-style firearms. These can perform fully automatic or burst fire. Some machine pistols even include a foldable shoulder stock to help the user maintain accuracy.

The speed of these weapons is measured by their cyclic rate. This is the speed at which the firearm performs the cycle of firing, ejecting, loading, and cocking. Different purposes require different rates. Anti-aircraft machine guns require extremely high rates of fire to increase hit probability. Infantry support weapons often have much lower rates. For example, the MG34 is a general purpose machine gun from the WWII era. It uses a recoil-operated mechanism to function. While its theoretical cyclic rate is between 1,000 and 1,200 rounds per minute, it typically fires between 800 and 900 rounds per minute.

Continuous fire creates significant physical challenges, specifically regarding heat. Rapid firing generates high temperatures in the barrel and the rest of the structure. If fired indefinitely, the components will eventually suffer structural failure. Even semi-automatic firearms can overheat if they are fired continuously. For the MG34, continuous fire might cause the weapon to fail in only one minute. Additionally, the recoil from firing can make it difficult for a user to reacquire their sight picture. This physical movement reduces the effective rate of fire during use.

Because of their power, automatic firearms are strictly regulated. In most developed countries, possession is restricted to military or law enforcement members. In the United States, the National Firearms Act of 1934 and the Firearm Owners Protection Act of 1986 govern these weapons. The 1986 act banned civilian ownership of new machine guns. This means only previously registered weapons can be purchased. Prospective owners must pass a criminal background check through the Bureau of Alcohol, Tobacco, Firearms and Explosives. They must also pay a $200 federal tax to receive a legal revenue stamp. Many people now use a gun trust to help manage this registration process.