breechblock

A breechblock (or breech block) is the part of the firearm action that closes the breech of a breech loading weapon (whether small arms or artillery) before or at the moment of firing. It seals the breech and contains the pressure generated by the ignited propellant. Retracting the breechblock allows the chamber to be loaded with a cartridge. Breechblocks are categorised by the type or design of the mechanism by which it is locked or closed for firing. The firearm action more fully refers to the mechanism by which the operator actuates the opening and closing of the breech.

Variants

, double-barreled shotgun A way of closing the breech or chamber is an essential part of any breech-loading weapon or firearm. Perhaps the simplest way of achieving this is a break-action, in which the barrel, forestock and breech pivot on a hinge that joins the front assembly to the rear of the firearm, incorporating the rear of the breech, the butt and usually, the trigger mechanism. A breechblock is a separate component and is not a feature of the break-action. A breechblock must close against the rear of the breech for firing but be able to be retracted or otherwise moved for loading or unloading or to remove a spent cartridge. A breechblock is not a component of designs with multiple or moveable chambers such as revolvers, harmonica guns, Kalthoff repeaters, Kammerlader rifles or, split breech designs. Another "Fokker Split Breech Rotary Machine Gun, ca. 1930" was donated to Kentucky Military Treasures; according to the museum record it "proved unsuccessful because of its inability to seal breech cylinders". A couple of 1920s US patents by other inventors also proposed to use this principle. The British also experimented with the design in the 1950s for aircraft guns, without success. It has only been used successfully in low-pressure applications, such as the Mk 18 Mod 0 grenade launcher. |group=notes}} This article primarily addresses the matter of breechblock design, as opposed to the action, which relates more with how the mechanism is operated, even if the distinction is not always clear.

Side-hinged breechblock

A side hinged breechblock is used in the Snider-Enfield. Other firearms using this type of breechblock include the Warner carbine, the Joslyn rifle and the Tarpley carbine. The breechblock is hinged parallel to the axis of the barrel and swings away to the side to expose the breech. Firing force is contained by the rear of the breechblock bearing on the receiver.

Rotating drum

A rotating drum breechblock or rotary breech consists of a cylinder which rotates on an axis offset from the barrel. It is also known as a cannon breech because of association with some cannon designs. A longitudinal cut-out section or eccentric hole provides access to the breech. Rotating the cylinder then closes the breech. The geometry is not unlike the cylinder of a revolver. In the M1867 Werndl–Holub, the cylindrical breechblock is retained at the rear by the receiver. Mating faces can be profiled (i.e. not faced perpendicular to the axis of rotation) so that the breech tends to seal or fit more closely as it is closed. the Nordenfelt eccentric screw breech is a variation of this design. Instead of holding the breechblock between the breech at one end and the receiver at the other, in this design the breechblock is threaded around its circumference and is screwed into the breech until it meets the rear of the chamber. The breech is opened by rotating it a fraction of a full turn, until a hole through the breechblock aligns with the bore. The Magnum Research Lone Eagle pistol is a single-shot pistol chambered for rifle cartridges that also uses a rotating drum breechblock.

Peabody-Martini

Initially used in the Peabody rifle, it saw more widespread use in the Martini–Henry and the subsequent Martini–Enfield. It employs a breechblock with a rear hinged falling block design, in which the breech is opened by permitting the front of the breechblock to drop down while pivoting on its hinge. Firing force is transmitted through the knuckle of the hinge and does not act directly on the hinge pin. The breechblock design as has been called a falling or tilting block but omitting the role of the hinge can lead to ambiguities. It is also used in the Krag–Petersson rifle.

Notes

References

External links

Breech Mechanisms in artillery

Text derived from https://en.wikipedia.org/w/index.php?oldid=1373604185 under CC BY-SA 4.0; modifications have been made.

Names in other languages