# Action **The method and mechanism by which a [[firearm]] loads, fires, and extracts [[Cartridge|cartridges]].** The **action** of a [[firearm]] refers to the type of *mechanism* it uses to manipulate - load, fire, and extract - [[Cartridge|cartridges]]. The action of a firearm is ultimately characterised by how the *breech* is opened and closed. ## Single-shot action A firearm with *single-shot* action is completely unable to move the cartridge and relies on the operator to perform all manipulation of the cartridge into and out of the [[Firearm#Chamber|chamber]]. As the name implies they can only fire one shot per barrel before requiring manual reloading. ### Breechblock > [!NOTE] Breechblock action > Single-shot firearms with a *breechblock* as part of its action involves moving a *simple block* that serves to seal the breech. Typically a breechblock is moved by some form of lever. > - *Tilting block* - the breechblock is hinged at the rear and tilts down at the front to allow loading/unloading, tilting back up to lock the breech > - *Rolling block* - the breechblock is rolled by the operator into and out of firing position > - *Falling block* - the breechblock slides vertically downwards for loading/unloading and upwards to lock the breech > > ![[BreechblockAction.svg]] ### Break-action > [!NOTE] Break-action > A firearm with *break* action has a [[Firearm#Barrel|barrel]] assembly that is *hinged* allowing it to be rotated downwards relative to the [[Firearm#Stock|stock]] thus exposing or *breaking open* the breech, enabling the reloading of the weapon. > > Break-action designs are simple and compact and have no reciprocating components. However, they are also weaker than other actions as it often relies on a small latch to keep the breech closed during firing. > > ![[BreakAction.svg]] > *Break-action of a Winchester Model 21; when the barrel assembly (red) is tilted forward, the cartridges (blue) can be extracted* ### Bolt action > [!NOTE] Bolt-action > A *bolt-action* firearm requires the operator to directly manipulate the [[Firearm#Bolt|bolt]]. They are more common in repeating firearms and can be [[Action#Bolt-action|further classified]] based on the movement required by the operator to move the bolt. *** ## Repeating action A firearm with *repeating* action contains components that can move cartridges from a supply of ammunition, such as a [[Firearm#Magazine|magazine]], into the chamber. Repeating firearms can fire several shots before ammunition must be manually reloaded. ### Manual A repeating firearm with *manual* action requires the operator to be involved in at least some part of the cycling of the firearm. #### Single-action revolvers > [!NOTE] Single-action revolvers > [[Firearm Types#Revolver|Revolvers]] with *single-action* [[Firearm#Trigger|triggers]] have mechanisms which only releases the [[Firearm#Hammer|hammer]] when pulled. Thus, the operator must manually cock the hammer which typically also rotates the cylinder. #### Bolt-action > [!NOTE] Bolt-action > *Bolt-action* repeating firearms also requires the operator to *directly manipulate the bolt*, but does not require a new cartridge to be inserted into the chamber after every shot. They are further classified by the necessary movement to operate the bolt. ##### Rotating bolt In a bolt-action firearm with a *rotating bolt*, the bolt handle must be *rotated upwards* before being pulled to the rear. The rotation of the bolt unlocks it from the breech. After unlocking the bolt, the handle is then pulled backwards thus opening the breech and allowing the spent cartridge to be extracted. Pushing the bolt forwards then chambers the next cartridge and rotating the bolt downwards locks the breech. ![[RotatingBolt.svg]] *Rotating bolt action of a Mosin-Nagant; the bolt (red) is rotated before it is pulled to the rear and the spent cartridge (blue) is extracted* ##### Straight pull A *straight pull* bolt-action firearm does not require the operator to rotate the bolt handle to unlock and lock the breech. Instead, extraction and unlocking can both be achieved by *linearly pulling back* the bolt handle. Pushing the bolt forwards then both chambers the next cartridge and locks the breech. ![[StraightPull.svg]] *Straight pull bolt action of a Mondragón rifle; the bolt handle (red) does not rotate and pulls the bolt (orange) straight backwards to allow the cartridge (blue) to be extracted* *** #### Pump-action > [!NOTE] Pump-action > A *pump-action* firearm involves a *sliding handguard or grip* beneath the barrel which the operator must *pump* in order to extract and chamber cartridges and cycle the action. > > The movement of the sliding grip backwards extracts and ejects spent cartridge while returning the grip forwards chambers a new cartridge. > > Typically, pump-action is employed in [[Firearm Types#Shotgun|shotguns]]. > > ![[PumpAction.svg]] > *Pump-action of a [[SPAS-12]]; the sliding grip (red) is pumped backwards which pushes the bolt (orange) to the rear via the cocking slide (pink); chambering not fully shown* #### Lever-action > [!NOTE] Lever-action > *Lever-action* firearms have an *external lever* which must be manually operated to extract and chamber cartridges and cycle the action. Typically, the lever is also the trigger guard, if not close to it. > > ![[LeverAction.svg]] > *Lever-action of a Winchester 1873; the trigger guard lever (red) actuates mechanical linkages (pink) which cycles the action (orange) and changes the cartridges (blue)* ### Autoloading A repeating firearm with *autoloading* action is capable of extracting and chambering cartridges and cycling the action on its own using the energy from firing a round. #### Blowback operation > [!NOTE] Blowback operation > In *blowback* operation, the action is cycled using the *energy from the combustion* in the chamber pushing backwards on the cartridge case. It differs from recoil operation as the breech is not locked when a round is fired. > > Blowback operation actions are further classified into simple or delayed blowback and more specifically into the method of delay. ##### Simple blowback *Simple blowback*, or *straight blowback*, is the most basic type of blowback operation and relies on gases from the combustion pushing the cartridge case and bolt backwards. It does not have anything except the mass of the bolt and the recoil spring slowing the rearward movement of the bolt. ![[SimpleBlowback.svg]] *Straight blowback action of an [[UZI]]; the cartridge case (blue) pushes backwards on the bolt (red, cutaway) due to the combustion; also shown is the recoil spring assembly (pink)* ##### Delayed blowback In a firearm with *delayed blowback* operation, the rearward movement of the bolt is *mechanically delayed* such that the breech is only opened after the internal pressure of the chamber is at a safe level. In any delayed blowback action, the delaying mechanism causes the force from the combustion to accelerate a component besides the bolt, usually the bolt carrier, to a *greater velocity than the bolt itself*. Thus, the rearward movement of the bolt is delayed. The most common types of delayed blowback is roller-delayed and lever-delayed. - *Roller-delayed* - a pair of rollers on the sides of the bolt initially sitting in notches in the frame are pushed inward as the bolt travels backwards - *Lever-delayed* - a lever between the bolt and the bolt carrier mechanically disadvantages the bolt, pushing the bolt carrier faster backwards than the bolt ![[RollerDelayedBlowback.svg]] *Roller-delayed blowback of an [[MP5]] viewed from above; as the bolt head (orange) is pushed back the rollers (red) are forced inward by the frame and pushes the bolt head carrier (pink) back* ![[LeverDelayedBlowback.svg]] *Lever-delayed blowback of a FAMAS; the bolt (orange) acts as the effort and the bolt carrier (pink) acts as the load on the lever (red) which rotates as the bolt carrier group moves backward* *** #### Recoil operation > [!NOTE] Recoil operation > In *recoil* operation, the action is also cycled using the *energy from the combustion* in the chamber pushing backwards on the cartridge case. However, the *breech is locked* and both the bolt and the barrel move from the recoil to some extent. > > Recoil operation actions are distinguished based on the distance of travel before the breech is unlocked. ##### Long recoil In *long recoil* operation, the bolt and barrel are locked together until *they reach the rear* due to recoil. The bolt is then held at the rear and unlocked from the barrel which then returns forward. The bolt is then allowed to return forward when the barrel is completely forward. ![[LongRecoil.svg]] *Long recoil action of a Browning Auto-5; the bolt (orange) and the barrel (red) are locked together until they reach the rear, after which the barrel is allowed to travel forwards on its own* ##### Short recoil In *short recoil* operation, the bolt and barrel are only locked together for a *short distance* under recoil. After the barrel stops, the bolt is allowed to travel on its own completely to the rear before returning forward. Short recoil operation is by far the most common action in semi-automatic [[Firearm Types#Pistol|pistols]]. ![[ShortRecoil.svg]] *Short recoil action of an [[M1911]]; the slide (orange), serving as the bolt, and the barrel (red) are locked only for a short distance before the barrel fully tilts and unlocks from slide* *** #### Gas operation > [!NOTE] Gas operation > In *gas* operation, the action is cycled by *high pressure gas* from the combustion that is *redirected* from a hole in the barrel back to the action. > > Gas operation actions involve either long or short-stroke pistons or direct impingement. ##### Long-stroke piston A firearm with *long-stroke* gas operation has a piston attached to the bolt carrier group and whose movement is responsible for the *entire cycle of the action*. Its main advantage is the greater positivity of the extraction and chambering of cartridges and the locking of the breech due to the higher momentum from the mass of the piston. However, this mass also more severely disrupts the point of aim with its movement. ![[LongStrokePiston.svg]] *Long-stroke gas operation of an [[AK-47|AKM]]; the piston is integral to the bolt carrier group (red) which carries the bolt (orange)* ##### Short-stroke piston A firearm with *short-stroke* gas operation has a piston that is separate from the bolt carrier group and moves only a short distance, imparting the energy from the gases in a *short impulse*. Its advantages are greater accuracy due to a smaller amount of moving mass in the action and greater reliability as hot gases do not enter the [[Firearm#Receiver|receiver]]. ![[ShortStrokePiston.svg]] *Short-stroke gas operation of a [[G36]]; the piston (red) travels a small distance and gives the bolt carrier (pink) a short impulse* ##### Direct impingement In *direct impingement*, the high pressure gases are redirected towards and directly impinges on the bolt carrier group with no components in between. Its main advantage is the simpler and lighter design as there does not need to be additional components to move and transfer the energy of the gases. The lack of moving parts besides the bolt carrier group also increases accuracy. The main disadvantage is the introduction of hot combustion gases directly into the cycling mechanism which can lead to quicker degradation. ![[DirectImpingement.svg]] *Direct impingement of an [[M4 Carbine]][^1]; the gas rod (dark blue) carries the gases directly to the bolt carrier (pink) which carries the bolt (orange)* [^1]: Some authors refer to the action in the M4 Carbine and [[M16]] as the "Stoner expanding gas system" exclusively instead of direct impingement. This is in reference to the fact that the gases are *channelled into the bolt carrier* where their expansion pushes the bolt carrier away from the bolt. However, under the above definition of direct impingement, the gases are still directly impinging on the bolt carrier.