Telescoping bolt

Internal mechanisms of the above submachine guns. Barrels are blue, bolts are green.

Atelescoping bolt(also known as anoverhung bolt) is a firearmboltwhichtelescopesover, that is, wraps around and past, thebreechend of the barrel. This feature reduces the required length of a weapon such as asubmachine gunsignificantly, and it allows compact designs to be balanced around the pistol grip in a way that gives "pointability" more like a pistol's.

While it would be simpler and easier to shorten the bolt to fit completely behind the breech, the bolt must have a certain amount of mass in order to operate reliably with a given caliber. The telescoping bolt moves some of that mass forward of the bolt face, resulting in a bolt which may be longer overall, but is shorter behind the bolt face.

Though technically a different, distinct concept, nearly all telescoping bolt submachine guns use amagazinelocated in the pistol grip used to hold and fire the weapon. However, there are blowback firearms with the magazine located in the grip that do not use a telescoping bolt, such asKel-Tec SUB-2000.

History

The telescoping bolt concept first appeared onsemi-automatic handgunsaround the turn of the 20th century. These pistols, starting with theFN M1900and to continuing to the present, often feature aslide,which acts as both abarrel shroudand the bolt. Moreover, a Belgian pocket pistol patented in 1909^[1]featured a cylindrical bolt wrapped around the barrel instead of a now-conventional slide, which is sometimes claimed to be the first true telescoping bolt design.^[2]

The first production model submachine gun using the telescoping bolt concept was the CzechoslovakCz 23 aka Sa.23 or vz.48b series,first produced in 1948. These submachine guns use a cylindrical telescoping bolt with centered barrel. While widely exported in the third world, the Cz 23 series was not well known in the west.^[3]

The first popularly well-known example was theUzi submachine gun,designed in Israel byUziel Gal,a designer inspired by the Cz 23 series. It uses a rectangular bolt, with a barrel which is offset toward the bottom of the bolt. This configuration places the axis ofrecoillower, increasing the controllability of the weapon in full-automatic fire. The Uzi was designed in 1948 after the first models of the Cz 23 were seen, and entered service in 1954 (after official adoption in 1951).

The telescoping bolt has subsequently been used in a wide variety of submachine gun designs.

Comparisons

As the image diagrams demonstrate, the basic concept of a telescoping bolt with the magazine well in the handgrip produces significantly more compact weapons. These diagrams show the 1938 design (1939 service)MP-40submachine gun, which is 630 mm (25 inch) long with the stock folded, weighing four kilograms (8.8 pounds) and having a 251 mm (9.9 inch) barrel, and the (similar materials and production technology) Uzi, a 1948 design (1951 adoption with 1954 service), which is 470 mm (19 inch) long with the stock folded, weighing 3.5 kilograms (7.7 pounds) and having a 260 mm (10.2 inch) barrel.

Utilizing nothing more than a configuration change, and the same materials and fabrication technologies, the Uzi is thus 500 grams (1.1 lb) lighter and 160 mm (6 inches) shorter overall, despite having a longer barrel by 9 mm (0.3 inch).

Examples

References

^GB 190920277
^https://littlegun.be/arme%20belge/artisans%20identifies%20e%20f/a%20fab%20armes%20reunies%20gb.htm
^Back to the Roots Archived2006-11-28 at theWayback Machine,Monty Mendenhall, at[1],accessed Jan 10, 2007

[1] GB 190920277

[2] ttps://littlegun.be/arme%20belge/artisans%20identifies%20e%20f/a%20fab%20armes%20reunies%20gb.htm

[3] Back to the Roots Archived2006-11-28 at theWayback Machine,Monty Mendenhall, at[1],accessed Jan 10, 2007

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