Letter O

The Definition of Over-Under

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Over-Under

Can also be spelled Over/Under, OverUnder or Over and Under. A firearm (most commonly a shotgun) with two barrels that are vertically aligned with each other, one on top of the other.


19 Other Firearms Definitions You Need To Know


Electronic Firing

The use of an electric current to fire a cartridge, instead of a percussion cap. In an electronic-fired firearm an electric current is used instead to ignite the propellant, which fires the cartridge as soon as the trigger is pulled.

Caseless Ammunition

A type of small arms ammunition that eliminates the cartridge case that typically holds the primer, propellant, and projectile together as a unit.

Factory Ammo

Ammunition that has been assembled by a commercial vendor of ammunition and sold in retail stores. This is as opposed to Hand loads which have been assembled by individuals and are not typically sold.

Crosshairs

The cross-shaped object seen in the center of a firearm scope. Its more-proper name is reticle.

Damascus Barrels

Barrel tubes built up by twisting alternate strips of iron and steel around a fixed rod (mandrel) and forge-welding them together in varying combinations according to the intended quality and the skill of the maker. The rod was withdrawn, the interior reamed and the exterior filed until the finished tube was achieved. Damascus barrels may be recognized by any of a variety of twist or spiral patterns visible in the surface of the steel. Before the 20th century, barrels were typically built in this manner because gunmakers did not have the technology to drill a deep hole the full length of a bar of steel without coming out the side.

Pinfire

An early form of complete, self-contained cartridge. It included bullet, powder and ignition primer, all in one package. The primer was located towards the base of the cartridge, but completely internally. The pin, shaped like a little finishing nail, pointed on the inside end and resting on the internal primer, projected radially about a quarter-inch to the outside of the base of the cartridge. When loaded, a pinfire gun showed the tips of the pins exposed through small slots in the tops of the breech faces of the barrels. To fire, hammers fell on the pins, driving them (through the wall of the cartridge) into the internal primer.

Mortar

An artillery piece used to fire shells over short ranges at very high trajectories.

Hand-Detachable Locks

The firing mechanism of a break-open gun which may be removed for inspection or cleaning without the use of tools. The release latch may be plainly visible or concealed. A feature typically seen on sidelock guns but also on the Westley Richards "droplock" boxlock action.

Scope

A magnifying tube through which the shooter may see the target and aim the firearm. Scopes contain a reticle, commonly in the shape of a cross, which must be properly centered upon the target for accurate aim.

Gas Vent

A passage built into a firearm to allow the safe conduct of unexpected gas, as from a pierced primer, to minimize damage both to the gun and to the shooter.

Bore

The tunnel down the barrel of a firearm through which the projectiles travel.

  • A smooth-bore firearm is one that does not have rifling on the barrel's internal surface.
  • A big-bore firearm is one that fires a large caliber.
  • A small-bore firearm is one that fires a small caliber.

Comb

The top of a gun's stock, where a shooter rests his cheek when mounting a gun. As it is the top of the stock that determines the position of one's eye, and one's eye is the rear sight on a shotgun, the position of the comb is very important in determining the proper fit of a shotgun.

Armor-Piercing Ammunition

An armor-piercing shell must withstand the shock of punching through armor plating. Shells designed for this purpose have a greatly strengthened case with a specially hardened and shaped nose, and a much smaller bursting charge.

Mauser Action

The premier bolt action, whose design by Paul Mauser coalesced in 1898, and from which were derived the Springfield 1903, the Winchester Model 70 and many others.

Sleeved Barrels

An economical method of bringing new life to a damaged pair of barrels, regardless of their original method of jointing. The ribs are removed. The barrels are cut off 3" - 4" from the breech end and discarded. The bores of the remaining breech-end are reamed out oversize. New tubes are fitted down into the original breech section and filed down to fit flush. The original ribs are then replaced. Sleeving is considerably less expensive than building a completely new set of barrels. Much of the time required to build a set of barrels is concentrated in the fitting of the breech end to the receiver; this work is salvaged through sleeving. Sleeving can be recognized by a pair of circumferential lines around the barrels a few inches from the breech; the more invisible, the finer the job. A sleeved gun should always be identified as such amongst the proof marks, and if done in England must be properly reproofed. Photo Sleeving is not the same thing as Monoblocking.

Duelling Pistols

Single shot pistols, of a design originating in England, in vogue circa 1770 - 1850, built necessarily in pairs, either of flintlock or percussion ignition, usually finely made and cased together with loading accessories. Dueling pistols tended to be lighter and sleeker than their contemporary service pistols. They tended to have smoothbore (or sometimes secret, scratch-rifling), octagon (or octagon-to-round) barrels around nine or ten inches long of some form of damascus steel, bores just over a half-inch, ramrods, rudimentary sights front and rear, single-set triggers, roller-bearing frizzens and curved grips integral with full or half-stocks. They were usually of high quality construction, sometimes with silver furniture, but normally of relatively plain decoration.

Doglock

The lock that preceded the 'true' flintlock in both rifles and pistols in the 17th century. Commonly used throughout Europe in the 1600s, it gained popular favor in the British and Dutch military. A doglock carbine was the principal weapon of the harquebusier, the most numerous type of cavalry in the armies of Thirty Years War and the English Civil War era.

Clip

A clip IS NOT a magazine. A clip is used to load a magazine.
A clip is a simple, disposable narrow spring-lined channel-rail that is used to store multiple rounds of ammunition together as a unit, ready for insertion into the magazine of a repeating firearm. This speeds up the process of loading and reloading the firearm as several rounds can be loaded at once, rather than one round being loaded at a time. The term clip commonly refers to a firearm magazine, though this usage is absolutely completely totaly 100% incorrect. In the correct usage, a clip is used to feed a magazine or revolving cylinder, while a magazine or a belt is used to load cartridges into the chamber of a firearm. in which cartridges are supplied for military weapons. The shooter positions the clip vertically above the firearm's magazine, then pressing down with the thumb, slides the cartridges from the clip and down into the magazine.

Magazine Safety

A mechanism that prevents the gun from being able to fire when the magazine is removed from the gun, even if there is still a round in the chamber.