Mass closure

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The ground lock is a type of lock for an automatic firearm . It is characterized by the fact that the barrel and slide are not mechanically locked together. The closure is based on inertia ; Peter Dannecker describes it physically as a “ force- fit, dynamically locked lock”.

The mass lock is used with two types of lock drives. On the one hand as a back pressure loader , corresponding to the English term blowback operation ; The barrel is rigid, while the breech can be moved backwards and on the other hand as a blow forward (English for pre-pressure loader ) in which the barrel can be moved forwards, while the breech or the support plate is rigid. Both types of shutter drive are gas pressure chargers . Since the blow-forward principle is rarely used in practice, the bulk seal is usually implicitly understood in the literature as a bulk seal in the back pressure charger . This article is structured accordingly.

Mostly John Moses Browning , but also Hugo Schmeisser and Georg von Dormus are named as inventors . The principle of the mass lock is used in many variants, from small pocket pistols to heavy automatic cannons .

General

Animation: reloading process based on a bulk seal

In the case of a mass lock, the fixed barrel and movable lock are not mechanically interlocked. After the ignition of the propellant charge , the cartridge case including the closure moves backwards under pressure. The return speed of the bolt must be limited to such an extent that the case is sufficiently supported by the cartridge chamber as long as the bullet is moving in the barrel and there is high pressure there . Basically, the cartridges should slip back from the chamber at most the thickness of the cartridge base, otherwise the hollow case part is no longer supported and the case may tear.

After the bullet has left the barrel, the slide moves further backwards due to its inertia, whereby the cartridge case is completely pulled out of the cartridge chamber and ejected. The stored spring energy increases with greater compression of the spring. When the breech has given up all of its kinetic energy to the spring or hits a stop and is thus at its rear dead center, the spring accelerates it forwards again, with a new cartridge being fed from the magazine into the chamber.

The closure may zuschießend or aufschießend be constructed. A movable firing pin can be dispensed with in the case of samples with a closing design . Here a spike hits the cartridge's primer when the breech is closed.

A: Cartridge with normal bottom
B: Cartridge with undercut bottom for the pre-ignition

When classifying the physical drive principle of the closure, misunderstandings arise in the literature. A basic distinction is made between gas pressure chargers and recoil chargers . The mass lock works on the principle of the gas pressure charger. The combustion gases of the propellant charge spread in all directions. This gas pressure pushes the bullet forward on the one hand and pushes the case back on the other. A movement impulse of the projectile to generate a recoil is also not necessary. The ground seal also works very well with blank cartridges if a maneuver cartridge device greatly narrows the cross-section of the pipe mouth and thus the necessary gas pressure is built up. A recoil loader, on the other hand, needs a projectile movement to generate the recoil. Nevertheless, the mass shutter is sometimes mistakenly assigned to the recoil chargers. Alternatively, the designation as a back pressure loader , corresponding to the English term blowback operation for the mass closure, is possible.

It is essential for the bulk seal that the case, against which the cartridge chamber seals, also slides backwards at the same time. Jamming the case in the chamber would not transfer enough energy to the breech, with the result that the reloading process of the next cartridge would stop. While this works on its own with weak pistol ammunition, precautions must be taken with stronger ammunition. For this reason, early machine guns with a mass lock, such as the Austrian Schwarzlose machine gun or the Italian Breda 30, and above all machine guns, required oiled cases. The oiling brings with it big problems, so that one would like to do without them.

At the time of the Second World War, cartridge chambers with pressure compensation grooves appeared. In the US variant of the 20 mm Oerlikon cannon, the Mark 4, these grooves were introduced at the transition from the chamber to the barrel in order to improve extraction problems despite the case oiling. As a result of these grooves, the same high pressure prevails in the interior of the sleeve as in the grooves around it. As a result, the case is not pressed so hard against the walls of the cartridge chamber and can slide back more easily.

In order to avoid gas loss due to poor ligation and to prevent case tears in the chamber, the cases should be cylindrical or only slightly conical and not have a very pronounced shoulder on a bottle neck case, because the further the conical case protrudes from the chamber, the less it will be supported by the chamber. With Bergmann pistols, for example, gas losses occurred due to poor leaning, which reduced the performance of the weapon and could lead to malfunctions if soiled.

In order to support the case longer in the cartridge chamber from the walls, the cartridge chamber must be extended. The sleeves provided for this purpose have a special so-called undercut base (rebated rim), i.e. H. the bottom diameter is smaller than the cross section of the sleeve. This allows the extractor with the cartridge to move into the cartridge chamber.

Weapons with a simple mass lock are mainly suitable for pistol ammunition. For strong rifle cartridges such as the 7.62 × 51 mm NATO cartridge, additional mechanisms are required to delay the breech, the breech is then called a delayed mass lock . There is also the variant with pre-ignition - in which the cartridge ignites when the bolt is closed - which was used with automatic cannons.

variants

Simple mass closure

A: Starting position
B: Propellant charge ignites, slide is pushed backwards
C: Bullet leaves the barrel, slide opens completely, case is ejected

The technically simplest variant of a breech for an automatic weapon is the simple ground lock. It implements the principle of the mass lock without any further mechanisms. Thanks to this simple structure, guns with a mass lock are considered very reliable. The closure is very easy to maintain, which includes disassembly and cleaning.

The breech is braked by various forces: frictional resistance between the case and cartridge chamber, inertia of the breech mass, frictional resistance between the breech and the housing, and the restoring force of the closing and impact springs. The simple ground lock is therefore sometimes called a spring-mass lock or ground-spring lock . However, this is not technically correct, because the spring force with regard to the closure is very low, i.e. negligible. The closure works through its inertia .

Since the mass of the breech must be matched directly to the performance of the cartridge, the breech principle in handguns is more limited than in other breech designs. The more powerful the cartridge, the heavier the lock and the greater the spring force of the closing spring, which makes handling more difficult. That is why simple spring-mass locks are only used with relatively inefficient cartridges.

The simple mass lock has therefore proven itself especially with small-caliber weapons ( .22 short , .22 lfB , e.g. FN-Browning self-loading rifle cal 22 ), with pistols for rather weak cartridges (such as 6.35 mm Browning , 7.65 mm Browning , 9 mm short , 9 mm Makarow ) as well as when shooting submachine guns with stronger cartridges, such as 9 × 19 mm , .45 ACP or 7.62 × 25 mm TT . Typical successful pistols are the Walther PPK , FN Browning Model 1900 or the Makarow (PM) . Heavy locks and springs can be built into submachine guns, so they can also fire stronger ammunition. This is also used in rare cases in pistols with a simple ground lock, for example in the Astra 600 or the HK VP70 , which makes the pistols difficult to use.

With a few exceptions, all submachine guns used in the world wars and beyond have a mass lock. Examples are the German MP 18 and submachine gun 40 , the English Lanchester submachine gun and the Sten Gun or the Russian PPSch-41 , the Israeli Uzi or the US Thompson M1 (late war production) and MAC-10 .

Earth lock with advance ignition

Simpified schematic of blowback mechanism with advanced primer ignition.png

With the simple mass lock, the lock holds the cartridge in the chamber due to its mass. However, this can only be implemented in practice for relatively weak cartridges. The idea of pre-ignition is to use the kinetic energy as the slide is advanced to keep the cartridge in the chamber. The sealing mass can thus be significantly reduced.

Many firing submachine guns, starting with the first real submachine gun, the MP18, use this principle on a small scale. They ignite the cartridge at the last moment of the closing movement when the slide is less than 1 mm from the cartridge chamber. The specialist literature often refers to the breeches of these weapons as simple mass locks.

The Becker machine cannon and its successors, the 20 mm Oerlikon cannon , the Oerlikon FF , Polsten 20 mm Flak , MG FF and MK 108, used a ground lock with “real” advance ignition . In these weapons, the breech and the firing pin are connected by a mechanism. The firing pin is controlled by a type of rocker so that it moves out of the breech when the breech has covered a certain distance. But there are also other technical realizations to ignite the cartridge in advance. The MK 108 has an electric ignition.

The cartridge was already ignited while the breech was still advancing, about 12.5 mm before the breech reached the chamber. Thus, the kinetic energy of the breech already acted against the gas pressure of the recoil when closing. This led to a quieter function, and the sealing mass could also be reduced. The significantly earlier firing of the Becker automatic cannons was achieved using cases with an undercut base together with an extended cartridge chamber.

The weapons fired greased ammunition in order to achieve better lubrication of the cartridge case and the cartridge chamber.

Delayed mass closure

In the case of weapons with a delayed mass lock, additional forces help to brake the lock. These can be inertial forces or other frictional forces and forces acting in the opposite direction to the locking movement.

If the mass closure is delayed by inertia, the closure is in two parts; at the front the bolt head is movably connected to the control piece. The pressure on the front of the bolt head when the shot is fired causes it to recede to a minimum. This movement is transmitted to the control piece via a suitable mechanism and accelerates it strongly. In the return, this releases the locking of the bolt head and moves backwards with it, which triggers the reloading process. One of the first weapons with a delayed mass lock is the Schwarzlose machine gun , in which the bolt head is connected to the control piece via a knee joint hinged to the housing. The most modern application, the roller lock with a bolt head with laterally locked support rollers , is found in the Heckler & Koch HK G3 rifle . When firing, the rollers are pressed inwards onto a wedge located at the front of the control piece. This is accelerated backwards by the resulting vertical force component, which triggers the reloading process. Due to the horizontal movement, the weapon remains in the line of sight even during the reloading process.

Another technique was used with the German Volkssturmgewehr Spezial . It is based on tapping the barrel and directing the gas into a cylinder in which a piston slows the return of the breech as long as there is pressure.

literature

  • George M. Chinn: The Machine Gun. Bureau of Ordnance, Department of the Navy, Washington DC 1951, OCLC 2233158 . [8th]
  • Charles Q. Cutshaw: Tactical Small Arms of the 21st Century: A Complete Guide to Small Arms From Around the World. Gun Digest Books, 2011, ISBN 9781440227097 [9]
  • Wolfgang Pietzner: Waffenlehre, 1st edition: - Basics of system theory. Work on studies and practice in the Federal Border Guard, Part 4, Lübeck 1998, ISBN 3-930732-32-7 ( PDF ).
  • Peter Dannecker: Locking systems for firearms. dwj Verlags-GmbH, Blaufelden 2009, ISBN 978-3-936632-20-0

Individual evidence

  1. ^ Pietzner: Waffenlehre. 1998, pp. 42-46.
  2. ↑ Dannecker: locking systems of firearms . 2009, p. 26
  3. ↑ a b Jaroslav Lugs: Small arms . Volume I. 6th edition, Military Publishing House of the GDR , 1979, p. 302
  4. ↑ Dannecker: locking systems of firearms . 2009, pp. 468-46
  5. ^ F. Flanhardt, K. Harbrecht: Chapter Classification of automatic firearms in: Waffentechnisches Taschenbuch. 3rd edition, Rheinmetall , Düsseldorf 1977. pp. 243–245 [1]
  6. ↑ Dannecker: locking systems of firearms . 2009, p. 26
  7. ^ Pietzner: Waffenlehre. 1998, pp. 42-46.
  8. ↑ Dannecker: locking systems of firearms . 2009, p. 397
  9. ↑ Dannecker: locking systems of firearms . 2009, pp. 468-469
  10. ^ Heinz Dathan: Weapon theory for the Bundeswehr. (4th revised edition), Mittler & Sohn Verlag , 1980, ISBN 3-87599-040-4 , p. 72
  11. ↑ Dannecker: locking systems of firearms . 2009, pp. 468-46
  12. ↑ Chinn: The Machine Gun. 1951, Volume I, p. 231.
  13. ↑ Terry Wieland: Gun Digest Book of Classic American Combat Rifles. Verlag Krause Publications, 2011, ISBN 9781440230172 , p. 515 [2]
  14. ↑ Chinn: The Machine Gun. 1951, Volume I, p. 522.
  15. ↑ Philip Gutzman: Vietnam: Naval and Riverine Weapons. Verlag Lulu.com, 2010, ISBN 9780557177431 , p. 454 [3]
  16. ↑ http://www.navweaps.com/Weapons/WNUS_2cm-70_mk234.htm United States of America 20 mm / 70 (0.79 ") Marks 2, 3 & 4
  17. ^ Brian J. Heard: Handbook of Firearms and Ballistics: Examining and Interpreting Forensic Evidence. Verlag John Wiley & Sons, 2011, ISBN 9781119964773 , p. 174 [4]
  18. ↑ Chinn: The Machine Gun. Volume IV, 1951, p. 10.
  19. ^ Georg Ortenburg: Weapons of the Landsknechte 1871-1914. Bechtermünz, 2005, original 1992, ISBN 3828905218 , p. 78.
  20. ↑ Manfred R. Rosenberger , Katrin Hanné : From the powder horn to the rocket projectile: The history of small arms ammunition. Motorbuch Verlag, 1993, ISBN 3613015412 , pp. 150-151.
  21. ↑ Chinn: The Machine Gun. Volume IV, 1951, pp. 12-13.
  22. ^ A b Robert E. Walker: Cartridges and Firearm Identification Verlag CRC Press , 2013, ISBN 9781466588813 , p. 24 [5]
  23. ↑ Automatic weapons , United States Army Materiel Command , 1970 pp. 2-47 [6]
  24. ^ Pietzner: Waffenlehre. 1998, p. 43
  25. ↑ Dannecker: locking systems of firearms . 2009, pp. 293, 397
  26. ↑ Gerald Prenderghast: Repeating and Multi-Fire Weapons: A History from the Zhuge Crossbow Through the AK-47 , McFarland Verlag, 2018, ISBN 9781476631103 , p. 179 [7]
  27. ↑ Cutshaw: Tactical Small Arms of the 21st Century. 2011, p. 17.
  28. ↑ Cutshaw: Tactical Small Arms of the 21st Century. 2011, p. 17.
  29. ↑ Werner Eckhardt, Otto Morawietz: The hand weapons of the Brandenburg-Prussian-German army 1640-1945. Verlag Helmut Gerhard Schulz, Hamburg 1957, p. 203.
  30. ↑ Chinn: The Machine Gun. 1951, Volume I, p. 522
  31. ↑ Chinn: The Machine Gun. Volume IV, 1951, p. 30.
  32. ↑ Chinn: The Machine Gun. 1951, Volume I, pp. 558-560.
  33. ↑ Chinn: The Machine Gun. 1951, Volume I, p. 522.
  34. ↑ Chinn: The Machine Gun. Volume IV, 1951, p. 13.
  35. ↑ Chinn: The Machine Gun. 1951, Volume I, p. 522.
  36. ^ Pietzner: Waffenlehre. 1998, pp. 43-44