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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 chamber of a firearm is the cavity at the back end of a breechloading weapon's barrel or cylinder, where the ammunition is inserted before being fired. The rear opening of the chamber is the breech, and is sealed by the breechblock or the bolt. [1] [2]
A breechloader [1] [2] is a firearm in which the user loads the ammunition from the breech end of the barrel (i.e., from the rearward, open end of the gun's barrel), as opposed to a muzzleloader, in which the user loads the ammunition from the end of the barrel.
E.g. if the preponderance was quoted as 4 tons 2 + 1 ⁄ 2 cwt (4.2 t) as for the RML 17.72-inch "100-ton" gun, the breech end sat with that weight on its mounting, enough to ensure stability but not enough to hinder changes in elevation. The preponderance of British muzzle-loading guns was typically stamped on the end of one of the trunnions.
The cap has one closed end. Inside the closed end is a small amount of a shock-sensitive explosive material such as fulminate of mercury. The percussion cap is placed over a hollow metal "nipple" at the rear end of the gun barrel. Pulling the trigger releases a hammer, which strikes the percussion cap and ignites the explosive primer.
A thumb-operated cam latch at the rear of the breechblock held it shut when in closed position. The rack-type system extractor was withdrawn automatically as the breechblock was opened and snapped back at the end of its stroke. The firing pin was housed within the breechblock. The hammer nose was flattened to accommodate the firing pin.
For best results, the breech must be opened at the proper time, just as the forward momentum of the gases reaches its maximum, the peak flow. This means that bore extractors are normally used only on guns with semi-automatic or fully automatic actions, where the breech is opened and the shell ejected as part of the recoil process.
The recoil operation is a type of locked-breech action used in semi-automatic and fully automatic firearms. It also uses energy from the combustion in the chamber acting directly on the bolt through the cartridge head, but in this case the firearm has a reciprocating barrel and breech assembly, combined with a bolt that locks to the breech.