Firearm action

A view of the break-action of a typical double-barreled shotgun, with the action open and the extractor visible. The opening lever and the safety catch can also be clearly seen.

In firearms terminology, an action is the physical mechanism that manipulates cartridges and/or seals the breech. The term is also used to describe the method in which cartridges are loaded, locked, and extracted from the mechanism. Actions are generally categorized by the type of mechanism used. A firearm action is technically not present on muzzleloaders as all loading is done by hand. The mechanism that fires a muzzle-loader is called the lock.

Manual operation

Manual operation is a firearms term describing any type of firearm action that is loaded one shot at a time by the user rather than automatically. For example, break action is a form of manual operation using a simple hinge mechanism that is manually unlatched by the operator exposing the chamber(s) for reloading.

Single-shot

Dropping block

These are actions wherein the breechblock lowers or "drops" into the receiver to open the breech, usually actuated by an underlever. There are two principal types of dropping block: the tilting block and the falling block.

Tilting block

In a tilting or pivoting block action, the breechblock is hinged on a pin mounted at the rear. When the lever is operated, the block tilts down and forward, exposing the chamber. The best-known pivoting block designs are the Peabody, the Peabody-Martini, and Ballard actions.

The original Peabody rifles, manufactured by the Providence Tool Company, used a manually cocked side-hammer. Swiss gunsmith Friedrich Martini developed a pivoting block action by modifying the Peabody, that incorporated a hammerless striker which was cocked by the operating lever with the same single, efficient motion that also pivoted the block. The 1871 Martini-Henry which replaced the "trapdoor" Snider-Enfield was the standard British Army rifle of the later Victorian era, and the Martini was also a popular action for civilian rifles.

Charles H. Ballard's self-cocking tilting-block action was produced by the Marlin Firearms Company from 1875, and earned a superlative reputation among long-range "Creedmoor" target shooters. Surviving Marlin Ballards are today highly prized by collectors, especially those mounted in the elaborate Swiss-style Schützen stocks of the day.

Falling block

Ruger No. 1 single-shot falling-block rifle with action open

A falling-block action (also known as a sliding-block action) is a single-shot firearm action in which a solid metal breechblock slides vertically in grooves cut into the breech of the weapon and actuated by a lever. Examples of firearms using the falling block action are the Sharps rifle and Ruger No. 1.

Rolling block

In a rolling block action the breechblock takes the form of a part-cylinder, with a pivot pin through its axis. The operator rotates or "rolls" the block to open and close the breech; it is a simple, rugged and reliable design. Rolling blocks are most often associated with firearms made by Remington in the later 19th century; in the Remington action the hammer serves to lock the breech closed at the moment of firing, and the block in turn prevents the hammer from falling with the breech open.

Break-action

German "Drilling" Combination Gun

A break action is a type of firearm where the barrel(s) are hinged and can be "broken open" to expose the breech. Multi-barrel break action firearms are usually subdivided into over-and-under or side-by-side configurations for two barrel configurations or "combination gun" when mixed rifle and shotgun barrels are used.

Hinged block

The earliest metallic-cartridge breechloaders designed for general military issue began as conversions of muzzle-loading rifle-muskets. The upper rear portion of the barrel was filed or milled away and replaced by a hinged breechblock which opened upward to permit loading. An internal angled firing pin allowed the re-use of the rifle's existing side-hammer. The Allin action made by Springfield Arsenal in the US hinged forward; the Snider-Enfield used by the British opened to the side. Whereas the British quickly replaced the Snider with a dropping-block Peabody style Martini action, the US Army felt the trapdoor action to be adequate and followed its muzzleloader conversions with the new-production Springfield Model 1873, which was the principal longarm of the Indian Wars and was still in service with some units in the Spanish-American War.

Bolt action

Although bolt actions are usually associated with fixed or detachable box magazines, in fact the first general-issue military breechloader was a single-shot bolt action: the paper-cartridge Prussian Needle Gun of 1841. France countered in 1866 with its superior Chassepot rifle, also a paper-cartridge bolt action. The first metallic-cartridge bolt actions in general military service were the Berdan Type II introduced by Russia in 1870, the Mauser Model 1871, and a modified Chassepot, the Gras rifle of 1874; all these were single-shots.

Today most top-level smallbore match rifles are single-shot bolt actions.

Single-shot bolt actions in .22 caliber were also widely manufactured as inexpensive "boys' guns" in the earlier 20th century; and there have been a few single-shot bolt-action shotguns, usually in .410 bore.

Other actions

• The Ferguson rifle: British Major Patrick Ferguson designed his rifle, considered to be the first military breechloader, in the 1770s. A plug-shaped breechblock was screw-threaded so that rotating the handle underneath would lower and raise it for loading with ball and loose powder; the flintlock action still required conventional priming.
• The Hall rifle: First U.S. cavalry breechloader, originally made in flint but later made-in and converted-to percussion in 1830's-1840's. The breech section tilts up to accept a paper cartridge. Excellent machine-made construction, but still tended to leak gas at the breech.
• The Kammerlader: A crank-operated Norwegian firearm produced around the time of the Prussian Needle-gun. Originally used a paper cartridge. Later many were converted to rimfire; this was the first Norwegian breechloader.
• The Tarpley carbine: This is categorized into falling block action, but the breech block is hinged unlike the others.
• The M1867 Werndl-Holub: Variation of the rotating bolt-style action; uses primed metallic cartridge.
• The Morse Carbine: The mostly brass action is somewhat like Hall rifle, except it was designed to take a special centerfire cartridge. Very few of these were actually made and were constructed in the late 1850s.
• The Joslyn rifle:
• Rising Breech Carbine:

Repeater

Revolver

A revolver houses cartridges in a rotary cylinder and advances them in-line with the bore prior to each shot. Revolvers are most often handguns however examples of rifles and shotguns have been made. The cylinder is most often rotated by manipulation of the trigger and/or hammer although some are semi-automatic using recoil to rotate the cylinder and cock the hammer.

Bolt action

Barreled action for bolt-action rifle

In bolt action firearms, the opening and closing of the breech is operated manually by a bolt. Opening the breech ejects a cartridge while subsequently closing the breech chambers a new round. The three predominant bolt-action systems are the Mauser, Lee-Enfield, and Mosin–Nagant systems.

Lever-action

A Winchester Model 1873 lever-action rifle

Lever action firearms uses a lever to eject and chamber cartridges. An example of firearms using lever action are the Winchester Repeating Rifle and Marlin Model 1894.

Pump-action

A Winchester M1897, one of the first successful pump-action shotgun designs

In pump action or slide action firearms, a grip called the fore end is manually operated by the user to eject and chamber a new round. Pump actions are predominantly found in shotguns. An example of firearms using the pump action are the Remington 870 and Winchester Model 1897.

Falling block

The Krag-Petersson rifle is the only example; it is loaded by tubular magazine.

Other actions

• French Guycot Chain Rifle
• Kalthoff repeater
• Cockson repeater
• Belton flintlock
• The Jennings Magazine Rifle
• Meigs Sliding Guard Action Repeater
• Roper repeater

Automatic actions

Blowback operation

A schematic of the lever-delayed blowback mechanism used in the FAMAS assault rifle.

Blowback operation is a system in which semi-automatic and fully automatic firearms operate through the energy created by combustion in the chamber and bore acting directly on the bolt face through the cartridge.

Examples of blowback operation

• Simple blowback: Halcon M-1943, Uzi submachine gun, Varan PMX-80
• Lever-delayed blowback: FAMAS, Sterling 7.62, AA-52, 2B-A-40, TKB-517
• Roller-delayed blowback: SIG 510, HK MP5, HK P9, HK G3
• Gas-delayed blowback: Volkssturmgewehr 1-5, [[Heckler & Koch P7, Steyr GB
• Toggle-delayed blowback: Schwarzlose MG M.07/12, Luger rifle and Pedersen rifle
• Blish Lock: early Thompson submachine guns
• Hesitation locked: Remington 51 pistol
• Chamber-ring delayed blowback: Seecamp pistol

Blow-forward operation

Blow-Forward operation is where the firearm lacks a bolt but has a moving barrel that is forced forward by the friction of the projectile against a spring as means of reloading a fresh round.

Examples of blow-forward operation

• Hino Komuro M1908 Pistol
• Steyr Mannlicher M1894
• Schwarzlose Model 1908
• Special Operations Weapon

Recoil operation

Recoil operation is a type of locked-breech firearm action used in semi-automatic and fully automatic firearms. As the name implies, these actions use the force of recoil to provide the energy to cycle the action.

Examples of recoil operation

• Short-recoil: Colt M1911, MAB PA-15, Browning Hi-Power, HK USP, Glock pistols, Mamba Pistol, M2 Browning machine gun, MG42, Vz 52 pistol, M82 Barrett rifle
• Long-recoil: Browning Auto 5, Femaru STOP Pistol, Mars Automatic Pistol
• Inertia: some Benelli shotguns

Gas operation

Gas operation is a system of operation used to provide energy to semi-automatic and fully automatic firearms. In gas-operation, a portion of high pressure gas from the cartridge being fired is used to extract the spent case and chamber a new cartridge. There are three basic types: long stroke gas piston (where the gas piston goes the same distance as the operating stroke of the action parts, and is often attached to the action parts), short stroke gas piston (where the gas piston goes less than distance as the operating stroke of the action parts), and direct impingement (AKA "direct gas", "gas impingement", where there is no piston, and the gas acts directly on the action parts). A fourth type, now considered obsolete and ineffective, are those systems based on the Bang rifle that utilize a muzzle cap to capture gas after the bullet has left the barrel. While this system is successful in boosting the operating power of recoil operated guns, it is insufficient and too susceptible to fouling for use as the primary operating system.

Examples of gas operation

• Short-stroke gas piston: FN FAL, SAR-87, HK G36
• Long-stroke gas piston: M1 Garand, AK-47
• Direct impingement: MAS 49, M16, AG-42
• Gas trap: Gewehr 41, Bang M1922 rifle