Break open
From Wikipedia, the free encyclopedia
A break open firearm is one whose barrels are hinged, and rotate perpendicular to the bore axis to expose the breech and allow loading and unloading. Break open actions are universal in double-barrelled shotguns and combination guns, and are common in single shot rifles, pistols, and shotguns.
[edit] Advantages
The break open action is one of the most compact firearms actions. Since there are no parts to reciprocate, it is much shorter than a repeating firearm, and as built the break-open is generally more compact that other non repeating firearms such as the falling block and rolling block actions. This compactness means reductions in weight and size, compared to larger actions; this can also allow a longer barrel in a firearm of equivalent size.
Since the cartridge extractor or ejector is built into the barrel assembly on break open actions, the breech face is simple a flat plate with a hole for the firing pin to project. This makes break open actions ideal for interchangeable barrel firearms, such as the popular Thompson Center Arms Contender and Encore pistols. The simplicity of the break open design, especially external hammer types, also reduces the cost of manufacture. There are a number of companies, such as H & R Firearms, producing break open rifles at far lower costs than comparable bolt action rifles.
[edit] Disadvantages
The break open design is only suitable for non-repeating firearms. To get multiple shots requires multiple barrels; while this is fairly simple for shotguns, double rifles require very precise alignment of the barrels so they shoot to the same point of aim. Modern double rifles are very expensive, and designed for short range use; the barrels are often regulated for ranges under 100 yards (90 m) for use against dangerous game.
Break open actions are also not as inherently strong as other action types. The action is generally held closed by a single locking lug, usually below the barrel in a single shot or between the barrels of a double barrelled gun. This is not as strong as the bolt action design, which generally uses multiple locking lugs around the permieter of the bolt to provide an even distribution of the forces of firing. Since many break open rifles, such as the inexpensive H&R models, are build on large frames originally meant for shotguns, the action is very heavily built. Still, belted magnum cartridges such as .300 Winchester Magnum are generally only found in the highest quality, very expensive break open rifles.
Break open designs work best with rimmed cartridges, which can use a solid extractor. Rimless cartides require a spring-loaded extractor, which can slide out of the way for cartridge insertion, and spring back to engage the recessed rim. While these spring loaded extrators are found on even inexpensive models, the spring loaded extractor is not as strong as a solid extractor, and increases the chance of failure to extract.
