Gas-operated reloading

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Gas-operated firearm (long-stroke piston, e.g. AK-47). 1) gas port, 2) piston head, 3) rod, 4) bolt, 5) bolt carrier, 6) spring Gas-operated firearm unifilar drawing.png
Gas-operated firearm (long-stroke piston, e.g. AK-47). 1) gas port, 2) piston head, 3) rod, 4) bolt, 5) bolt carrier, 6) spring

Gas-operation is a system of operation used to provide energy to operate locked breech, autoloading firearms. In gas-operation, a portion of high-pressure gas from the cartridge being fired is used to power a mechanism to dispose of the spent case and insert a new cartridge into the chamber. Energy from the gas is harnessed through either a port in the barrel or a trap at the muzzle. This high-pressure gas impinges on a surface such as a piston head to provide motion for unlocking of the action, extraction of the spent case, ejection, cocking of the hammer or striker, chambering of a fresh cartridge, and locking of the action.

Contents

History

The first mention of using a gas piston in a single-shot breech-loading rifle comes from 1856, by the German Edward Lindner who patented his invention in the United States and Britain. [1] In 1866, Englishman William Curtis filed the first patent on a gas-operated repeating rifle but subsequently failed to develop that idea further. [2] Between 1883 and 1885, Hiram Maxim filed several patents on blowback-, recoil-, and gas-operation. In 1885, one year after Maxim's first gas-operated patent, a British inventor called Richard Paulson, who a year before had patented a straight blowback-operated rifle and pistol, again, one year after Maxim’s first blowback patent, patented a gas piston-operated rifle and pistol which he claimed could be used with sliding, rotating or falling bolts. He would also patent a gas-operated revolver in 1886. Paulson did construct models of his rifle and tried them in France shortly after filing his patent. [3] Furthermore, according to A. W. F. Taylerson, a firearms historian, his patented revolver was probably workable. [4] In 1887, an American inventor called Henry Pitcher patented a gas-operated conversion system that he claimed could be applied to any manually-operated magazine rifle. [5] In 1890 he would patent and submit an original gas-operated rifle for testing by the US government but it performed poorly and was ultimately never adopted despite being offered commercially for the civilian market. [6] In the 1880s a gas piston-operated rifle and pistol were developed by the Clair Brothers of France who received a French patent and submitted prototypes for testing by the French army in 1888 although the true date of their invention is uncertain. They would also produce a semi-automatic shotgun in the early 1890s. [7] [8] In 1889, the Austro-Hungarian Adolf Odkolek von Újezd filed a patent for the first successful gas-operated machine gun. [9]

Piston systems

Most current gas systems employ some type of piston. The face of the piston is acted upon by combustion gas from a port in the barrel or a trap at the muzzle. Early guns, such as Browning's "flapper" prototype, the Bang rifle, and the Garand rifle, used relatively low-pressure gas from at or near the muzzle. This, combined with larger operating parts, reduced the strain on the mechanism. To simplify and lighten the firearm, gas from nearer the chamber needed to be used. This high-pressure gas has sufficient force to destroy a firearm unless it is regulated somehow. Most gas-operated firearms rely on tuning the gas port size, mass of operating parts, and spring pressures to function. Several other methods are employed to regulate the energy. The M1 carbine incorporates a very short piston, or "tappet." This movement is closely restricted by a shoulder recess. This mechanism inherently limits the amount of gas taken from the barrel. The M14 rifle and M60 GPMG use the White expansion and cutoff system to stop (cut off) gas from entering the cylinder once the piston has traveled a short distance. [10] Most systems, however, vent excess gas into the atmosphere through slots, holes, or ports.

Gas trap

A gas trap system involves "trapping" combustion gas as it leaves the muzzle. This gas impinges on a surface that converts the energy to motion that, in turn, cycles the action of the firearm. As the resulting motion is forward toward the muzzle of the gun, some sort of mechanical system is needed to translate this into the rearward motion needed to operate the bolt. This adds to the complexity of the mechanism and its weight, and the placement of the trap generally results in a longer weapon and allows dirt to easily enter the mechanism. Despite these disadvantages, they use relatively low pressure gas and do not require a hole in the barrel, which made them attractive in early designs. The system is no longer used in modern weapons.

Hiram Maxim patented a muzzle-cup system in 1884 described in U.S. patent 319,596 though it is unknown if this firearm was ever prototyped. John Browning used gas trapped at the muzzle to operate a "flapper" in the earliest prototype gas-operated firearm described in U.S. patent 471,782 , and used a slight variation of this design on the M1895 Colt–Browning machine gun "potato digger". The Danish Bang rifle used a muzzle cup blown forward by muzzle gas to operate the action through transfer bars and leverage. Other gas-trap rifles were early production M1 Garands and German Gewehr 41 (both Walther and Mauser models).

The American and German governments both had requirements that their guns operated without a hole being drilled in the barrel. Both governments would first adopt weapons and later abandon the concept. Most earlier US M1 Garand rifles were retrofitted with long-stroke gas pistons, making the surviving gas trap rifles valuable in the collector's market.

In the 1980s Soviet designer Alexander Adov from TsKIB SOO modified the concept with a tube diverting gas from the muzzle to a standard long stroke system (see below) in order to diminish influence of the gas engine on barrel and increase accuracy, but his sniper rifle wasn't adopted due to the dissolution of the Soviet Union. [11]

Long-stroke

Diagram of long-stroke gas operation system Gas OPR.gif
Diagram of long-stroke gas operation system
Long stroke gas piston, from an AK-74 Longstrokegaspiston noBG.jpg
Long stroke gas piston, from an AK-74

With a long-stroke system, the piston is mechanically fixed to the bolt group and moves through the entire operating cycle. This system is used in weapons such as the Bren light machine gun, AK-47, Tavor, FN Minimi, FN MAG, FN FNC, and M1 Garand. The primary advantage of the long-stroke system is that the mass of the piston rod adds to the momentum of the bolt carrier enabling more positive extraction, ejection, chambering, and locking. The primary disadvantage to this system is the disruption of the point of aim due to several factors such as: the center of mass changing during the action cycle, abrupt stops at the beginning and end of bolt carrier travel, and the use of the barrel as a fulcrum to drive the bolt back. Also, due to the greater mass of moving parts, more gas is required to operate the system that, in turn, requires larger operating parts.

Short-stroke

short-stroke gas piston PISTONM16.gif
short-stroke gas piston
Short stroke gas piston and bolt carrier group, from a gas piston AR-15 Shortstrokegaspiston noBG.jpg
Short stroke gas piston and bolt carrier group, from a gas piston AR-15

With a short-stroke or tappet system, the piston moves separately from the bolt group. It may directly push [12] the bolt group parts, as in the M1 carbine, or operate through a connecting rod or assembly, as in the Armalite AR-18 or the SKS. In either case, the energy is imparted in a short, abrupt push and the motion of the gas piston is then arrested, allowing the bolt carrier assembly to continue through the operating cycle through kinetic energy. This has the advantage of reducing the total mass of recoiling parts compared with a long-stroke piston. This, in turn, enables better control of the weapon due to less mass needing to be stopped at either end of the bolt carrier travel and prevents hot combustion gases from being pushed into the internals and removes powder residue in the receiver which significantly improves reliability, increasing the lifespan of weapon parts by reducing instances of malfunctions under prolonged periods of extreme high rate of fire and suppressed shooting. The short-stroke operating system is available both on military (HK416 lineage, LMT MARS) and civilian markets as an alternative or retrofit to the AR-15 family of weapons for addressing the shortcomings of the Stoner internal gas piston operating system.

Short-stroke fixed

It is a cross between a short-stroke gas piston and a M1 Garand type long-stroke gas piston system. It is similar to a regular short-stroke piston in operation because it too uses an open gas piston that has an impingement cavity at its head, that rests on a gas block on the barrel. However just like the long-stroke gas piston system used on the M1 Garand the piston assembly is integrated with the operating rod and moves with the bolt group.

The caveat of this system is that it has heavier moving mass than modern long-stroke gas piston systems used on rifles like the AK-47, Tavor, FN FNC, etc. Hence firearms using this system do have higher felt recoil than their equivalent modern long-stroke gas piston counterparts.

Gas-delayed blowback

The bolt is not locked but is pushed rearward by the expanding propellant gases as in other blowback-based designs. However, propellant gases are vented from the barrel into a cylinder with a piston that delays the opening of the bolt. It is used by Volkssturmgewehr 1-5 rifle, the Heckler & Koch P7, Steyr GB and Walther CCP pistols.

Floating chamber

floating chamber Kinematik Gasdrucklader Kammerhub Schwenkriegel CC BY-SA 4.0 by Grasyl.svg
floating chamber

To avoid consuming a lot of relatively expensive rounds, many armies, including the United States Army, trained machine gun crews with less-expensive sub-caliber ammunition in the late 19th century and the first half of the 20th century. To do this, they needed a cheap .22 LR cartridge to operate firearms designed to use the .30-06 cartridge. David Marshall Williams invented a method that involved a separate floating chamber that acted as a gas piston with combustion gas impinging directly on the front of the floating chamber. [13] The .22 caliber Colt Service Ace conversion kit for the .45 caliber M1911 pistol also used Williams' system, which allows a much heavier slide than other conversions operating on the unaugmented blowback mechanism and makes training with the converted pistol realistic. A floating chamber provides additional force to operate the heavier slide, providing a felt recoil level similar to that of a full power cartridge. [14]

Direct impingement

direct impingement DIRECTM16.gif
direct impingement

The direct impingement (DI) method of operation vents gas from partway down the barrel through a tube to the working parts of a rifle where they directly impinge on the bolt carrier. This results in a simpler, lighter mechanism. Firearms that use this system include the French MAS-40 from 1940, the Swedish Ag m/42 from 1942. The Stoner gas system of the American M16, M4, and AR-15 style rifles utilize a modified version of this where a gas tube delivers gas into the bolt carrier to impinge on the bolt, which acts as a piston to cycle the rifle. One principal advantage is that the moving parts are placed in-line with the bore axis meaning that sight picture is not disturbed as much. This offers a particular advantage for fully automatic mechanisms. It has the disadvantage of the high-temperature propellant gas (and the accompanying fouling) being blown directly into the action parts. [15] Direct impingement operation increases the amount of heat that is deposited in the receiver while firing, which can burn off and cover up lubricants. The bolt, extractor, ejector, pins, and springs are also heated by the same high-temperature gas. These combined factors reduce service life of these parts, reliability, and mean time between failures. [16]

Other uses of gas in firearms

Animation of the Vickers muzzle booster operation, showing the expanding gases pushing the barrel to the rear relative to the cooling jacket VickersMuzzleBoosterAnim.GIF
Animation of the Vickers muzzle booster operation, showing the expanding gases pushing the barrel to the rear relative to the cooling jacket

Several other uses have been found for exhaust gases other than to aid cycling:

Muzzle booster
The French Chauchat, German MG 34 and MG 42 machine guns, the British Vickers machine gun, and some other recoil operated firearms use a gas trap style mechanism to provide additional energy to "boost" the energy provided by recoil. This "boost" provides higher rates of fire and/or more reliable operation. It is alternately called a "gas assist", and may also be found in some types of blank-firing adapters.
Gas ejection
Patented by August Schüler, the Reform pistol featured a vertical row of barrels that advanced upwards with each shot exposing the fired chamber. As the lower barrel fired, a gas hole between the barrels pressurized the empty barrel enough to eject the case rearward. An extended spur on the hammer prevented the spent case from hitting the firer in the face. The final case required manual extraction.

See also

Related Research Articles

<span class="mw-page-title-main">Semi-automatic rifle</span> Type of autoloading rifle

A semi-automatic rifle is an auto-loading rifle that fires a single cartridge with each pull of the trigger. It uses part of the fired cartridge's energy to eject the case and automatically loads another cartridge into its chamber. This is in contrast to bolt-action or lever-action rifles, which will require the user to manually chamber a new round before they can fire again, and fully automatic rifles, which fire continuously while the trigger is held down.

<span class="mw-page-title-main">Action (firearms)</span> Functional mechanism of breech-loading

In firearms terminology, an action is the functional mechanism of a breech-loading firearm that handles the ammunition cartridges, or the method by which that mechanism works. Actions are technically not present on muzzleloaders, as all those are single-shot firearms with a closed off breech with the powder and projectile manually loaded from the muzzle. Instead, the muzzleloader ignition mechanism is referred to as the lock.

A semi-automatic firearm, also called a self-loading or autoloading firearm, is a repeating firearm whose action mechanism automatically loads a following round of cartridge into the chamber and prepares it for subsequent firing, but requires the shooter to manually actuate the trigger in order to discharge each shot. Typically, this involves the weapon's action utilizing the excess energy released during the preceding shot to unlock and move the bolt, extracting and ejecting the spent cartridge case from the chamber, re-cocking the firing mechanism, and loading a new cartridge into the firing chamber, all without input from the user. To fire again, however, the user must actively release the trigger, and allow it to "reset", before pulling the trigger again to fire off the next round. As a result, each trigger pull only discharges a single round from a semi-automatic weapon, as opposed to a fully automatic weapon, which will shoot continuously as long as the ammunition is replete and the trigger is kept depressed.

<span class="mw-page-title-main">Gewehr 41</span> Battle rifle

The Gewehr 41 English: Rifle 41, commonly known as the G41(W) or G41(M), denoting the manufacturer (Walther or Mauser), are two distinct and different battle rifles manufactured and used by Nazi Germany during World War II. They were largely superseded by the Gewehr 43, which was derived from the G41(W), but with an improved gas system and other detail changes.

A repeating rifle is a single-barreled rifle capable of repeated discharges between each ammunition reload. This is typically achieved by having multiple cartridges stored in a magazine and then fed individually into the chamber by a reciprocating bolt, via either a manual or automatic action mechanism, while the act of chambering the round typically also recocks the hammer/striker for the following shot. In common usage, the term "repeating rifle" most often refers specifically to manual repeating rifles, as opposed to self-loading rifles, which use the recoil, gas, or blowback of the previous shot to cycle the action and load the next round, even though all self-loading firearms are technically a subcategory of repeating firearms.

<span class="mw-page-title-main">Direct impingement</span> Type of gas operation for a firearm

Direct impingement is a type of gas operation for a firearm that utilizes gas from a fired cartridge to impart force on the bolt carrier or slide assembly to cycle the action. Firearms using direct impingement are theoretically lighter, more accurate, and less expensive than firearms using cleaner and cooler gas piston systems.

Blowback is a system of operation for self-loading firearms that obtains energy from the motion of the cartridge case as it is pushed to the rear by expanding gas created by the ignition of the propellant charge.

<span class="mw-page-title-main">Rotating bolt</span> Method of locking used in firearms

Rotating bolt is a method of locking the breech of a firearm closed for firing. Johann Nicolaus von Dreyse developed the first rotating bolt firearm, the "Dreyse needle gun", in 1836. The Dreyse locked using the bolt handle rather than lugs on the bolt head like the Mauser M 98 or M16. The first rotating bolt rifle with two lugs on the bolt head was the Lebel Model 1886 rifle. The concept has been implemented on most firearms chambered for high-powered cartridges since the 20th century.

<span class="mw-page-title-main">Ferdinand Mannlicher</span> Austrian firearms designer (1848 - 1904)

Ferdinand Ritter von Mannlicher was an Austrian engineer and small arms designer. Along with James Paris Lee, Mannlicher was particularly noted for inventing the en-bloc clip charger-loading box magazine system. Later, while making improvements to other inventors' prototype designs for rotary-feed magazines, Mannlicher, together with his protégé Otto Schönauer, patented a perfected rotary magazine design, the Mannlicher–Schönauer rifle, which was a commercial and military success.

<span class="mw-page-title-main">Bolt (firearms)</span> Mechanical part of a firearm

A bolt is the part of a repeating, breechloading firearm that blocks the rear opening (breech) of the barrel chamber while the propellant burns, and moves back and forward to facilitate loading/unloading of cartridges from the magazine. The firing pin and extractor are often integral parts of the bolt. The terms "breechblock" and "bolt" are often used interchangeably or without a clear distinction, though usually, a bolt is a type of breechblock that has a nominally circular cross-section.

<span class="mw-page-title-main">Locked breech</span>

Locked breech is the design of a breech-reloading firearm's action. This is important in understanding how a self-reloading firearm works. In the simplest terms, the locked breech is one way to slow down the opening of the breech of a self-reloading firearm when fired. The source of power for the movement is recoil.

<span class="mw-page-title-main">Caliber conversion device</span> Device used to allow a firearm to fire a different cartridge

A caliber conversion device is a device which can be used to non-permanently alter a firearm to allow it to fire a different cartridge than the one it was originally designed to fire. The different cartridge must be smaller in some dimensions than the original design cartridge, and since smaller cartridges are usually cheaper, the device allows less expensive fire practice.

<span class="mw-page-title-main">Pedersen rifle</span> Semi-automatic rifle

The Pedersen Rifle, officially known in final form as the T1E3 rifle, was a United States semi-automatic rifle designed by John Pedersen that was made in small numbers for testing by the United States Army during the 1920s as part of a program to standardize and adopt a replacement for the M1903 Springfield.

A muzzle booster or recoil booster is a device fixed to the muzzle of a firearm, intended to harness the energy of the escaping propellant to augment the force of recoil on portions of the firearm. In spite of its name, a muzzle booster does not increase muzzle force or velocity but instead is usually used to improve the reliability and/or rate of fire of a recoil operated firearm. It was invented by Hiram Maxim in 1894.

<span class="mw-page-title-main">Blank-firing adapter</span> Firearms safety device for projectile-less cartridges

A blank-firing adapter or blank-firing attachment (BFA), sometimes called a blank adapter or blank attachment, is a device used in conjunction with blank ammunition for safety reasons, functional reasons or a combination of them both. Blank firing adapters are required for allowing blank ammunition to cycle the bolts of most semi-automatic and automatic firearms. It can also be a safety feature designed to break up the plugs replacing the bullet in military blanks as well as divert the hot gases from a blank discharge out to the sides, reducing the risk of injury to the target of an aimed shot.

<span class="mw-page-title-main">Mendoza RM2</span> Light machine gun

The Mendoza RM2 was a light machine gun similar to the M1918 BAR manufactured in Mexico by Productos Mendoza, S.A. Rafael Mendoza have been producing machine guns for the Mexican Army since 1933 and all have been noted for their lightness, simplicity, ease of maintenance, and economic construction without sacrificing reliability.

The StG 45(M) (abbreviation of Sturmgewehr 45, "Assault Rifle 45") sometimes referred to as the MP 45(M), was a prototype assault rifle developed by Mauser for the Wehrmacht at the end of World War II, using an innovative roller-delayed blowback operating system. It fired the 7.92×33mm Kurz (or "Pistolenpatrone 7.9mm") intermediate cartridge at a cyclic rate of around 450 rounds per minute.

The following are terms related to firearms and ammunition topics.

Recoil operation is an operating mechanism used to implement locked-breech autoloading firearms. Recoil operated firearms use the energy of recoil to cycle the action, as opposed to gas operation or blowback operation using the pressure of the propellant gas.

<span class="mw-page-title-main">Repeating firearm</span> Firearms that can be discharged multiple times after a single ammunition reload from its magazine

A repeating firearm or repeater is any firearm that is capable of being fired repeatedly before having to be manually reloaded with new ammunition from the magazine.

References

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  10. U.S. patent 1,907,163
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  12. U.S. patent 2,090,656 Page 8, column 2, lines 67–70, Pg 9, column 1, lines 22–39
  13. Charles E. Petty, "Delightful diversion: testing Kimber's new rimfire was a tough job, but someone had to do it", Guns Magazine, March 2004. Contains some discussion about the floating chamber device.
  14. S. P. Fjestad (1991). Blue Book of Gun Values (13th ed.). p. 291. ISBN   0-9625943-4-2.
  15. Smith, W.H.B.; Ezell, E. C. (1983), Small Arms of the World, 12th Edition, Stackpole Company, Harrisburg PA
  16. Major Thomas P. Ehrhart Increasing Small Arms Lethality in Afghanistan: Taking Back the Infantry Half-Kilometer. US Army. 2009