Bolt action

Opened bolt on a Winchester Model 70. The bolt has an engine turned finish.

Bolt action is a type of firearm action in which the weapon's bolt is operated manually by the opening and closing of the breech (barrel) with a small handle, most commonly placed on the right-hand side of the weapon (for right-handed users). As the handle is operated, the bolt is unlocked, the breech is opened, the spent cartridge case is withdrawn and ejected, the firing pin is cocked (this occurs either on the opening or closing of the bolt, depending on design), and finally a new round/cartridge (if available) is placed into the breech and the bolt closed. Bolt-action firearms are most often rifles, but there are some bolt-action shotguns and a few handguns as well. Examples of this system date as far back as the early 19th century, notably in the Dreyse needle gun. From the late 19th century, all the way through both World Wars, the bolt-action rifle was the standard infantry firearm for most of the world's militaries.

In military and law enforcement use, the bolt action has been mostly replaced by semi-automatic and selective-fire firearms, though the bolt action remains the dominant design in dedicated marksman rifles. Bolt-action firearms are still very popular for hunting and target shooting. Compared to most other manually operated firearm actions, it offers an excellent balance of strength (allowing powerful cartridge chamberings), ruggedness, reliability, and potential accuracy, all with light weight and much lower cost than self-loading firearms, and can also be disassembled and re-assembled much faster due to fewer moving parts. The major disadvantage is a slightly lower practical rate of fire than other manual repeating firearms, such as lever-action and pump-action firearms, and a far lower practical rate of fire than semi-automatic weapons, but this is not a very important factor in many types of hunting, target shooting, and other precision-based shooting uses.

History

The first bolt-action rifle was produced in 1824 by Johann Nikolaus von Dreyse, following work on breechloading rifles that dated to the 18th century. Von Dreyse would perfect his Nadelgewehr (Needle Rifle) by 1836, and it was adopted by the Prussian Army in 1841. It became the first bolt-action weapon to see combat in 1864. The United States purchased 900 Greene rifles (an under-hammer, percussion-capped, single-shot bolt action that utilized paper cartridges and an ogivial-bore rifling system) in 1857, but this weapon was ultimately considered too complicated for issue to soldiers and was supplanted by the Springfield rifle, a conventional muzzle loading rifle. During the American Civil War, the bolt-action Palmer carbine was patented in 1863, and by 1865, 1000 were purchased for use as cavalry weapons. The French Army adopted its first bolt-action rifle, the Chassepot rifle, in 1866 and followed with the metallic-cartridge bolt-action Gras rifle in 1874 .

European armies continued to develop bolt-action rifles through the latter half of the Nineteenth Century, first adopting tubular magazines as on the Kropatschek rifle and the Lebel rifle, a magazine system pioneered by the Winchester rifle of 1866. Ultimately the military turned to bolt-action rifles using a box magazine; the first of its kind was the M1885 Remington–Lee, but the first to be generally adopted was the British 1888 Lee–Metford. The Mauser Gewehr 98 was considered the epitome of this type of action, and its descendents became the standard against which all such rifles are measured. World War I marked the height of the bolt-action rifle's use, with all of the nations in that war fielding troops armed with various bolt-action designs.

During the buildup prior to World War II, the military bolt-action rifle began to be superseded by the semi-automatic rifle and later assault rifles, though bolt-action rifles remained the primary weapon of most of the combatants for the duration of the war; and many American units, especially USMC, used bolt-action '03 Springfields until sufficient M1 Garands were available. The bolt action is still common today among sniper rifles, as the design has potential for superior accuracy, reliability, lesser weight, and the ability to control loading over the faster rate of fire that alternatives allow. There are however, many semi-automatic sniper rifle designs, especially in the designated marksman role.

Today, bolt-action rifles are chiefly used as hunting rifles. These rifles can be used to hunt anything from vermin, to deer, to large game, especially big game caught on a safari, as they are adequate to deliver a single lethal shot from a safe distance.

Bolt-action shotguns are considered a rarity among modern firearms, but were formerly a commonly used action for .410 entry-level shotguns, as well as for low-cost 12 gauge shotguns. The M26 Modular Accessory Shotgun System (MASS) is the most advanced and recent example of a bolt-action shotgun, albeit one designed to be attached to an M16 rifle or M4 carbine using an underbarrel mount (although with the standalone kit, the MASS can become a standalone weapon). Mossberg 12 gauge bolt-action shotguns were briefly popular in Australia after the 1997 firearms law changes, but the shotguns themselves were awkward to operate and only had a three-round magazine, thus offering no practical and real advantages over a conventional double-barrel shotgun.

Some pistols utilize a bolt action, although this is uncommon, and such examples are typically specialized target handguns.

Major bolt-action systems

There are three major bolt-action system designs: the Mauser system, the Lee–Enfield system, and the Mosin–Nagant system. All differ in the way the bolt fits into the receiver, how the bolt rotates as it is being operated, the number of locking lugs holding the bolt in place as the gun is fired, and whether the action is cocked on the opening of the bolt (as in the Mauser system) or the closing of the bolt (as in the Lee–Enfield system). The vast majority of bolt-action rifles utilize one of these three systems, with other designs seeing only limited use.

Mauser

A disassembled Karabiner 98k action

Main article: Mauser

The Mauser M 98 bolt system was introduced in the Mauser Gewehr 98 and is the most common bolt-action system in the world, being in use in nearly all modern hunting rifles and the majority of military bolt-action rifles until the middle of the 20th century. The Mauser system is stronger than that of the Lee–Enfield with its two locking lugs just behind the bolt head better able to handle higher pressure cartridges (i.e. "Magnum" calibre centrefire rifle cartridges), while the Lee–Enfield or Mosin–Nagant actions require some strengthening to do the same task. A novel safety feature was the introduction of a third locking lug present at the rear of the bolt that normally did not lock the bolt, since it would introduce asymmetrical locking forces. The Mauser system features "cock on opening", meaning the upward rotation of the bolt when the rifle is opened cocks the action. A drawback of the Mauser M 98 system is that it can not be cheaply mass-produced very easily. Many Mauser M 98 inspired derivatives feature technical alterations, such as omitting the third safety locking lug, to simplify production.

The controlled-feed Mauser M 98 bolt-action system's simple, strong, safe, and well-thought-out design inspired other military and hunting/sporting rifle designs that became available during the 20th century, including the:

• Gewehr 98/Karabiner 98k
• vz. 24/vz. 33
• Type 24 rifle
• M1903 Springfield
• Pattern 1914 Enfield
• M1917 Enfield
• Arisaka Type 38/Type 99
• M48 Mauser
• FR8
• modern hunting/sporting rifles like the CZ 550, Heym Express Magnum, Winchester Model 70 and the Mauser M 98
• modern sniper rifles like the GOL Sniper Magnum and Zastava M07

Versions of the Mauser action designed prior to the Gewehr 98's introduction, such as that of the Swedish Mauser rifles and carbines, lack the third locking lug and feature a "cock on closing" operation.

Lee–Enfield

Close-up of the action on an SMLE Mk III rifle, showing the bolt-head, magazine cut-off, and charger clip guide.

Main article: Lee–Enfield

The Lee–Enfield bolt-action system was introduced in 1889 with the Lee–Metford and later Lee–Enfield rifles (the bolt system is named after the designer and the barrel rifling after the Royal Small Arms Factory at Enfield), and is a "cock on closing" action in which the forward thrust of the bolt cocks the action. This type of bolt can be used on modern magnum rounds and is found in several bolt-action .50 BMG rifles today. Since the Lee–Enfield's locking lugs are at the rear of the bolt, repeated firing over time can lead to receiver "stretch" and excessive headspace; accordingly, the Lee–Enfield bolt system features a removable bolthead, which allows the rifle's headspace to be adjusted by simply removing the bolthead and replacing it with one of a different length as required. In the years leading up to WWII, the Lee–Enfield bolt system was used in numerous commercial sporting and hunting rifles manufactured by such firms in the UK as BSA, LSA, and Parker–Hale, as well as by SAF Lithgow in Australia. Vast numbers of ex-military SMLE Mk III rifles were sporterised post-WWII to create cheap, effective hunting rifles, and the Lee–Enfield bolt system is used in the M10 and No 4 Mk IV rifles manufactured by Australian International Arms.

• Lee–Enfield (all marks and models)
• Ishapore 2A1
• Various hunting/sporting rifles manufactured by BSA, LSA, SAF Lithgow, and Parker-Hale
• Australian International Arms M10 and No 4 Mk IV hunting/sporting rifles

Mosin–Nagant

Main article: Mosin–Nagant

The Mosin–Nagant action, created in 1891, differs significantly from the Mauser and Lee–Enfield bolt action designs. The Mosin–Nagant design has a separate bolthead which rotates with the bolt and the bearing lugs, in contrast to the Mauser system where the bolthead is a non-removable part of the bolt. The Mosin–Nagant is also unlike the Lee–Enfield system where the bolthead remains stationary and the bolt body itself rotates. The Mosin–Nagant bolt is a somewhat complicated affair, but is extremely rugged and durable; it, like the Mauser, uses a "cock on open" system. Like the Lee–Enfield bolt system, the Mosin–Nagant system can be suitable for use with modern "Magnum" calibre centrefire rifle cartridges (the BOHICA Arms .50 BMG being one), although it is worth noting that its standard Russian 180-grain 7.62×54mmR ammunition is comparable to some loadings of the 7mm Remington Magnum. Although this bolt system has been rarely used in commercial sporting rifles (the Vostok brand target rifles being the most recognized) and never outside of Russia, large numbers of military surplus Mosin–Nagant rifles have been sporterized for use as hunting rifles in the years since WWII.

One interesting aspect of the Mosin–Nagant rifle's long and varied history comes from the wars for independence between Finland and the Soviet Union. Large numbers of these Mosin–Nagant rifles, some Russian, and some made by foreign countries such as France and even America for Tsarist Russia, were inherited and then re-worked by Finland into various models prior to WWII. The Finnish M28 is widely considered to be one of the finest and most accurate military rifles ever produced; Simo Häyhä, one of the most successful military snipers of all time, recorded over 500 kills with a standard-issue Finnish M28 Mosin–Nagant rifle over the course of about 100 days. Häyhä accomplished this feat without the use of a scope, as he preferred iron sights.

Straight-pull

The Mannlicher M95/30

In addition to the most common bolt-action systems, others have been devised that failed to achieve the ubiquity of the Mauser, Lee–Enfield, and Mosin–Nagant designs. Some of the most notable of these are the Canadian Ross rifle, the Swiss Schmidt–Rubin and Austro-Hungarian Mannlicher M1895 designs. All three are straight-pull bolt actions, but are entirely unrelated designs. 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, 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.

More recently the Blaser company has introduced a new straight-pull action where locking is achieved by a series of concentric 'blades'.

In the sport of biathlon, straight-pull actions are quite common, and are used almost exclusively on the world cup along with the Lateral Toggle action. The first company to make the straight pull action for .22 caliber was JG Anschutz; the action is specifically the straight pull ball bearing lock action, which features spring-loaded ball bearings on the side of the bolt which lock into a groove inside the bolt's housing. With the new design came a new dry-fire method; instead of the bolt being turned up slightly, the action is locked back to catch the firing pin. The two companies who have made the lateral toggle are Finn biathlon, as well as Izhmash. Finn was the first to make this type of action, however, due to the large swing of the arm as well as the stiffness of the bolt, these rifles fell out of favour and have been discontinued. Izhmash improved on the lateral swing with their Biathlon 7-3 and 7-4 series rifles, which have some use on world cups, but are largely thought of as inaccurate as well as having the inconvenience of having to remove the shooter's hand from the grip. Semiautomatic actions are illegal for race use.

Other designs

Another notable design is the Norwegian Krag–Jørgensen, which was used by Norway, Denmark, and briefly the United States. It is unusual among bolt-action rifles in that is loaded through a gate on right side of the receiver, and thus can be reloaded without opening the bolt. The Norwegian and Danish versions of the Krag have two locking lugs, while the American version has only one. In all versions, the bolt handle itself serves as an emergency locking lug. The Krag's major disadvantage compared to other bolt-action designs is that it is usually loaded by hand, one round at a time, although a box-like device was made that could drop five rounds into the magazine, all at once. This made it slower to reload than other designs which used stripper or en-bloc clips. Another historically important bolt-action system was the Gras system, used on the French Mle 1874 Gras rifle and the Mle 1886 Lebel rifle, which was first to introduce ammunition loaded with nitrocellulose-based smokeless powder.

Operating the bolt

Typically, the bolt consists of a tube of metal inside of which the firing mechanism is housed, and which has at the front or rear of the tube several metal knobs, or "lugs", which serve to lock the bolt in place. The operation can be done via a rotating bolt, a lever, cam-action, locking piece, or a number of systems. Straight-pull designs have seen a great deal of use, though manual turn-bolt designs are what is most commonly thought of in reference to a bolt-action design due to the type ubiquity. As a result, the bolt-action term is often reserved for more modern types of rotating bolt-designs when talking about a specific weapon's type of action. However, both straight-pull and rotating bolt rifles are types of bolt-action rifles. Lever-action and pump-action weapons must still operate the bolt, but they are usually grouped separately from bolt-actions that are operated by a handle directly attached to a rotating bolt. Early bolt-action designs, such as the Dreyse needle gun and the Mauser Model 1871, locked by dropping the bolt handle or bolt guide rib into a notch in the receiver, this method is still used in .22 rimfire rifles. The most common locking method is a rotating bolt with two lugs on the bolt head, which was used by the Lebel Model 1886 rifle, Model 1888 Commission Rifle, Mauser M 98, Mosin–Nagant and most bolt-action rifles. The Lee–Enfield has a lug and guide rib, which lock on the rear end of the bolt into the receiver.

Loading

Most bolt-action firearms are fed by an internal magazine loaded by hand, by en bloc, or stripper clips, though a number of designs have had a detachable magazine or independent magazine, or even no magazine at all, thus requiring that each round be independently loaded. Generally, the magazine capacity is limited to between two and ten rounds, as it can permit the magazine to be flush with the bottom of the rifle, reduce the weight, or prevent mud and dirt from entering. A number of bolt-actions have a tube magazine, such as along the length of the barrel. In weapons other than large rifles, such as pistols and cannons, there were some manually operated breech loading weapons. However, the Dreyse Needle fire rifle was the first breech-loader to use a rotating bolt design. Johann Nicholas von Dreyse's rifle of 1838 was accepted into service by Prussia in 1841, which was in turn developed into the Prussian Model 1849. The design was a single-shot breech loader, and had the now familiar arm sticking out from the side of the bolt, to turn and open the chamber. The entire reloading sequence was a more complex procedure than later designs, however, as the firing pin had to be independently primed and activated, and the lever was only used to move the bolt.

Benefits and drawbacks

Bolt-action firearms can theoretically achieve higher muzzle velocity and therefore have more accuracy than semi-automatic rifles because of the way the barrel is sealed. In a semiautomatic rifle, some of the energy from the charge is directed towards ejecting the spent shell and loading a new cartridge into the chamber. In a bolt action, the shooter performs this action by manually operating the bolt, allowing the chamber to be better sealed during firing, so that much more of the energy from the expanding gas can be directed forward. However, numerous other factors related to design and ammunition affect reliability and accuracy, and well designed modern semi-automatic rifles can be exceptionally accurate. Because of the combination of relatively light weight, reliability, high potential accuracy and lower cost, the bolt action is still the design of choice for many hunters, target shooters and marksmans.

The bolt action's locking lugs are normally at the front of the breech (some designs have additional "safety lugs" at the rear), and this increases potential accuracy relative to a design which locks the breech at the rear, such as a lever action. Also, a bolt action's only moving parts when firing are the pin and spring. Since it has fewer moving parts and a short lock time, it has less of a chance of being thrown off target and/or malfunctioning.

Because the spent cartridge is removed by manual action rather than automatically ejected, it can help a marksman remain hidden. Because the cartridge is not visibly flung into the air and onto the ground, a bolt action may be less likely to reveal a shooters position. Also, the cartridge can be removed when most prudent, allowing the shooter to remain still until reloading is tactically feasible. Bolt actions are also easier to operate from a prone position than other manually repeating mechanisms and work well with box magazines which are easier to fill and maintain than tubular magazines.

The integral strength of the design means very powerful magnum cartridges can be chambered without significantly increasing the size or weight of the weapon. For example, some of the most powerful elephant guns are in the same weight range (7–10 lbs.) as a typical deer rifle, while delivering several times the kinetic energy to the target. The recoil of these weapons, however, is correspondingly severe. One well known example is bolt-action rifles designed for the .223 Remington, which can usually safely fire the more powerful 5.56×45mm NATO, while auto-loaders might malfunction. By contrast, the operating mechanism of a semi-automatic weapon must increase in mass and weight as the cartridge it fires increases in power. This means that semi-automatic rifles firing magnum cartridges tend to be relatively heavy and impractical for many types of hunting.

The bolt action requires four distinct movements and is therefore generally slower than other major manual repeating mechanisms, such as lever and pump action, which generally require two movements, although straight-pull bolt actions also require only two distinct movements. Also, the trigger hand must leave the gun and regrip the weapon after each shot, usually resulting in the shooter having to realign his sight and reacquire the target for every shot. It is also not ambidextrous, and left-handed models tend to be more expensive.

Safety and headspace

On used bolt-action firearms, especially, the headspace should be checked with headspace gauges prior to shooting to ensure it is correct, and to prevent over-stressing chambers and cartridge brass. Some bolt-action rifles, such as the Lee–Enfield, have a series of different length bolts available to extend the service life of the rifle, for taking up any wear of the bolt and chamber occurring from long years of service. In the case of the No. 4 Lee–Enfield bolt, the bolt heads themselves are replaceable separate from the bolt and are marked 0, 1, 2, or 3, with each bolt head in sequence being nominally 0.003" longer than the bolt head numbered one less, for easily taking up any action stretching that may have occurred. It is possible to replace such a bolt head without tools by disassembling the bolt from the action, unscrewing the bolt head, and replacing the bolt head with the next higher number bolt head, for restoring a safe headspace.

The interrelated mechanics of safe trigger function, correct headspace, and equal bearing of the locking lugs requires that the bolt and action assembly are factory "fitted". Usually shown by the rifle serial number, applied to both bolt and action, indicating they are a matched pair. Accidental or deliberate swapping of bolts between similar rifles is not unusual, but is potentially dangerous. Any rifle with mismatched action/bolt serial numbers should be considered to be unsafe to fire until checked and so marked by a competent gunsmith or armourer.

Furthermore, there are many subtle issues involving the provenance of a rifle and its ammunition. Many calibres have dual civilian/military uses but are not completely identical - e.g. the .308 Winchester/7.62mm NATO and .223 Remington/5.56mm NATO have very slight differences in chamber sizes. Military ammunition often has thicker brass, and harder primers. Over major wars there were literally millions of surplus rifles converted to civilian uses (sporterized), many may be unsafe with modern ammunition - caution is required with any ex-military bolt action.

Other Firearm Actions

• Lever-action
• Pump-action
• Break-action
• Falling-block action
• Rolling block
• Semi-automatic rifle

See also

• Antique guns
• Blowback (arms)
• British military rifles
• Browning A-Bolt
• Carcano
• Gas-operated
• K31
• Krag–Jørgensen
• KNT-308
• Lebel rifle
• M1903 Springfield rifle
• M1917 Enfield rifle
• Mannlicher–Schönauer
• MAS-36
• Mosin–Nagant
• Mosquefal
• Recoil operation
• Remington 700
• Ruger M77
• Spencer repeating rifle
• Weatherby
• Winchester Model 70
• Service rifle
• Rotating bolt