Action (firearms)

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 functional mechanism of a breech-loading weapon that handles (loads, locks, fires, extracts and ejects) the ammunition, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot weapons with a closed off breech and the ammunition is manually loaded through the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock, (e.g. matchlock, flintlock, caplock etc).

Actions can be categorized in several ways, including single action versus double action, break action versus bolt action, and others. The term action can also include short, long, and magnum if it is in reference to the length of the rifle's receiver and the length of the bolt. The short action rifle usually can accommodate a cartridge length of 2.8 in (71 mm) or smaller. The long action rifle can accommodate a cartridge of 3.34 in (85 mm), and the magnum action rifle can accommodate cartridges of 3.6 in (91 mm), or longer in length.

Single shot actions

Diagram of various firearm actions

Breechblock

Dropping block

The dropping block 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

Main article: Tilting bolt

In a tilting block 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

Main article: Falling-block action

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

Main article: 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.

Hinged block

The hinged block used in 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.

Break-action

Main article: Break action

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.

Bolt action

Main article: Bolt action

Although bolt-action guns 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.

Eccentric screw action

The eccentric screw action first seen on the M1867 Werndl–Holub and later on the Magnum Research Lone Eagle pistol, the breech closure is a rotating drum with the same axis, but offset from the bore. When locked, a firing pin aligns with the primer and the breech is otherwise solid. When rotated open, a slot in the drum is exposed for extraction and feeding of a new round. Though first used on the Werndl-Holub, this action is commonly known as a cannon breech due to its association with the French 75mm Model of 1897 cannon. The French M1897 was, itself, based on William Hubbell's U.S. Patent 149,478.

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 1830s–1840s. 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 Morse Carbine: This mostly brass action is somewhat like the Hall rifle, except it was designed to take a special centerfire cartridge. Very few of these were actually made; all were constructed in the late 1850s.
• The Joslyn rifle:
• Rising Breech Carbine:

Repeating actions

Manual operation

Revolver

Main article: Revolver

Smith and Wesson M&P revolver

A revolver is a multi-chamber (but single-barrelled) firearm that houses cartridges in a rotary cylinder which indexes each round into alignment with the barrel bore (with the help of a forcing cone) prior to each shot. Revolvers are most often handguns; however, examples of revolving rifles, shotguns and cannons have been made. The cylinder is most often rotated via linkage to a manually manipulated hammer, although some revolvers are "double action" using the manual pull of the trigger to drive the cylinder rotation and hammer cocking.

Bolt action

Barreled action for bolt-action rifle

Main article: Bolt action

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.

Straight-pull action

US Navy M1895 straight pull rifle

In the Mauser-style turn-bolt action, the bolt handle must be rotated counter-clockwise, drawn rearward, pushed forward, and finally rotated clockwise back into lock. In a straight-pull action, the bolt lever can be cycled without rotating it, hence producing a reduced range of motion by the shooter from four movements to two, with the goal of increasing the rifle's rate of fire. The Ross and Schmidt–Rubin rifles load via stripper clips, albeit of an unusual paperboard and steel design in the Schmidt–Rubin rifle, while the Mannlicher uses en-bloc clips. The Schmidt–Rubin series, which culminated in the K31, are also known for being among the most accurate military rifles ever made. Yet another variant of the straight-pull bolt action, of which the M1895 Lee Navy is an example, is a camming action in which pulling the bolt handle causes the bolt to rock, freeing a stud from the receiver and unlocking the bolt.

Pump-action

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

Main article: Pump-action

In pump action or slide action firearms, a sliding grip at the fore-end beneath the barrel 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.

Lever-action

Main article: Lever-action

The lever-action firearms use a linked lever to eject and chamber cartridges. An example of firearms using lever action are the Winchester Repeating Rifle, the Henry rifle and the Marlin Model 1894.

Bolt release

The bolt release or lever release action is a hybrid repeating action that uses the physical manipulation of a bolt release lever/button to complete the cartridge chambering process. However, unlike the lever action (which demands the shooter's hand to actually provide the force needed for cycling the action), bolt release firearms eject the used cartridge automatically without involving the lever, usually via blowback or gas operation, and often uses a spring-assisted mechanism to chamber the next round. However, after moving rearwards the bolt is stopped by a bolt catch and will not move back into battery position and chamber the new round, until the user manually disengage the catch by depressing a release lever/button. Due to the fact that the action cannot complete its loading cycle without manual input from the user, it is technically a manually operated action rather than a self-loading one.

Whilst the basic principle can be traced back to other self-ejecting rifles, such as the single-shot Harrington & Richardson Model 755 rifle, this action has since been popularized in the United Kingdom by Southern Gun Company, who manufacture with "Manually Actuated Release System" (MARS) action rifles/pistol-caliber carbines in .223, .308, 9mm and .45 ACP calibers, as the interrupted mechanism complies with The Firearms (Amendment) Act 1988 which bans possession of self-loading centrefire rifles. The French company Verney-Carron makes and exports the Speedline hunting rifle and the Véloce shotgun, which has caused some moral concern in the mainstream media in Australia due to lobbying by the Greens and anti-gun groups such as Gun Control Australia, with David Shoebridge quoting the term "semi-semi-automatic". Similarly, Savage Arms has introduced the A17R and A22R rimfire rifles (both modified from its new A-series rifles, with a bolt release lever in front of the trigger guard), aiming at the Australian market, but law enforcement agencies such as the Northern Territory Police has attempted to unilaterally defining these rifles as "linear repeating firearms with assisted ejection" and reclassify them as semi-automatic, and hence prohibited without at least a Category C license, which is off-limit to most urban and rural residents who do not own farms. In 2020, CZ also introduced CZ 515, a bolt-release modified version of the CZ 512, to the Australian market via its importer Winchester Australia. The Turkish manufacturer Pardus Arms also produces the 12 gauge-caliber BRS17 shotgun, which uses a bolt release button on the back of the receiver to chamber rounds before firing.

Other actions

• Rotary cannon: Gatling gun, M134 Minigun
• Chain gun: Hughes Chain Gun, Guycot Chain Rifle, Treeby chain gun
• Kalthoff repeater
• Cookson repeater
• Belton flintlock
• The Jennings Magazine Rifle
• Meigs Sliding Guard Action Repeater
• Roper repeater
• The Orvill Robinson Model 2 rifle: Orvill Robinson, a New York-based firearms designer, developed two rifles. His first, patented in 1870 and commonly referred to by collectors as the "Model 1" though it has no official designation, was a precursor to straight-pull bolt actions like the Mannlicher M1886. The second rifle designed by Robinson, patented in 1872, was very different, employing a double hinged action that folded upward from the receiver to remove the spent casing and back down and forward to chamber a new round. Though hammer-fired, it is recognizable as a manually actuated ancestor of the toggle action found in firearms such as the Luger Parabellum 1908 pistol or Pedersen Rifle.
• Krag-Petersson Rifle Though frequently classified as only single-shot firearms, one tilting block rifle usually falls under the category of repeating firearms. The user, upon ejecting a round from the chamber, would load a round from the underbarrel magazine onto the loading surface of the tilting block, then raise it to the mouth of the chamber where the user could then easily push it forward into the chamber. Though this would not meet most standards of "repeating" for most modern users, the classification has been in use historically.
• Remington-Rider Magazine Pistol has a manually-actuated rolling block action to pull a cartridge from a tubular magazine set below the barrel and simultaneously cock the weapon. The block was rolled back into battery, loading the cartridge into the chamber, by spring pressure while the hammer remained in the cocked position.

Remington Nylon 66 .22 Rimfire semi-automatic rifle

Autoloading operation

Blowback operation

Main article: Blowback (firearms)

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

The 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. In blowback operation the bolt is not locked to the chamber, relying only on spring pressure and inertia from the weight of the bolt to keep the action from opening too quickly. Blowback operation is used for low-powered cartridges due to the weight of the bolt required.

Delayed blowback actions use some mechanism to slow down rearward travel of the bolt, allowing this action to handle more powerful ammunition and/or reduced weight of the bolt.

Examples of blowback operation

• Simple blowback: Halcón 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, HK 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 Model 51 and R51 pistols
• Chamber-ring delayed blowback: Seecamp pistol

Blow-forward operation

Main article: Blow forward

The blow-forward operation uses a fixed breech and moving barrel that is forced forward relative to the breech by the friction of the projectile against the bore as well as the breech recoiling away from the barrel. The barrel is spring loaded and returns automatically to chamber a fresh round from the magazine. Examples of this action are the Steyr Mannlicher M1894, Hino Komuro M1908 Pistol and the Schwarzlose Model 1908.

Recoil operation

Main article: Recoil operation

The recoil operation is a type of locked-breech firearm action used in semi-automatic and fully automatic firearms. It also uses energy from the combustion in the chamber acting directly on the bolt through the cartridge head, but in this case the firearm has a reciprocating barrel and breech assembly, combined with a bolt that locks to the breech. The breech remains locked as the bolt and barrel travel rearward together for some distance, allowing pressure in the chamber to drop to a safe level before the breech is opened.

Examples of recoil operation

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

Gas operation

Main articles: Gas-operated reloading and Direct impingement

The gas operation is a system of operation mechanism 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 tapped through a hole in the barrel and diverted to operate the action. 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 travels a shorter distance than 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, FN FNC
• Direct impingement: MAS 49, M16, AG-42
• Gas trap: Gewehr 41, Bang M1922 rifle

See also

• Locked-breech
• Lock (firearm)
  • Matchlock
  • Wheellock
  • Flintlock
  • Caplock
• Trigger

External links

• How Small Arms Work – Training Movie on YouTube