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Glossary Gun Terms Beginning O and P

A design of breechloading action whereby the breech slides forward to the barrels (or vice versa) and the one overlaps the other to form a better seal. Ordinarily, modern firearms do not require special obturating breeches because ductile brass cartridges swell slightly when fired, effectively sealing the rapidly expanding gas within the breech.

The effect of the base of a bullet expanding under the pressure of the detonating powder charge to make a better seal within the bore of a firearm and to make for more efficient utilization of the propellant's energy.

The standing position for shooting a rifle from the shoulder. A stance generally not resulting in as fine accuracy as the other positions, kneeling, sitting and prone; but usually faster.

O/U or OVER AND UNDER [BARRELS] Over and under barrels are better than side-by-side barrels because they have a narrower sighting plane. They allow more precise aiming and allow slightly better peripheral vision. Over & under guns are more suitable for shooting clays, where one generally knows where and when the target will be presented.

A small oval plate of nickel, silver or gold, usually inletted flush into the underside of the buttstock of a fine gun on which the owner's initials, monogram or coat of arms may be engraved.

Full Pistol Grip, with flat knob, with or without pistol grip cap. Although less sleek in appearance than a straight English grip, a more naturally fitting handle allowing the human hand to hold the gun in a more relaxed position. Considered by many to be more suitable for target guns, where one shoots somewhat deliberately.

A handle, mounted to the underside of the forend of a rifle built for off-hand target shooting. In use, a right-handed person would place the butt to the shoulder, grasp the wrist with the right hand, cock the left elbow to the left hip and by triangulation of his forearm support the palmrest with the palm of his left hand.

A bulge in the side of the pistol grip of a stock designed fill the palm of the hand and offer the shooter a more comfortable, repeatable hold on his gun.

The shape of the shot cloud as it deploys from the muzzle of a shotgun. While choke determines the degree of concentration of the shot, it is primarily skilled boring of the barrel that determines the highly-desirable evenness of the pattern. Cartridge design can also effect evenness and concentration of pattern.

A stockmaking detail where a small metal component such as a sling swivel stud is mounted to a raised flat area.

A type of gunsight, mounted towards the rear of a rifle through which one simply looks, placing the front sight on the target. Also called an aperture sight. With a small aperture, it can be very accurate. With a larger aperture, it allows faster target acquisition. Typically adjustable for windage and elevation. It is superior to the open rear buckhorn or express sight because it requires the shooter to focus on two planes only (the front sight and the target) instead of three (the open rear sight, the front sight and the target. The attribute is especially beneficial for older people who have trouble focusing at near distances. And, the small aperture, by bending light rays at the edge of its metal-to-air interface, effectively acts as a lens.

A rifle or pistol using compressed air or CO2 to propel a skirted pellet as opposed to a spherical BB. Not a firearm.

Small spherical projectiles loaded in shotshells and more often called "shot." Also the skirted projectiles used in pellet guns.

A metal bar, available in a variety of lengths, with a continuous row of Weaver-like scope mount base slots, which when attached to a firearm, allow convenient attachment of a variety of sights, lights, slings, bipods and other accessories.

In Smith & Wesson parlance, a pin (in its American definition---a small-diameter cylinder of steel) fitted through the top front of a revolver frame and through the breech end of the barrel, to lock it into position after it has been screwed in place.

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.

A cylindrical loop affixed to the underside of a barrel, to retain a ramrod.

Synonymous with "handgun." A gun that is generally held in one hand. It may be of the single-shot, multi-barrel, repeating or semi-automatic variety and includes revolvers.

The handle of a handgun or protrusion on the buttstock or fore-end of a shoulder-operated gun that resembles the grip or handle of a handgun. A "semi-pistol grip" is one less pronounced than normal; a "vertical pistol grip" is more pronounced than normal.

The angle of the butt of a gun in relation to the line of sight. In America, pitch is measured by resting the gun with its butt flat on a floor, the top of the receiver against a wall and its muzzle pointing up. The distance of the muzzle from the wall is the gun's pitch down. In England, pitch is determined by measuring the length of pull, separately, to each of the heel, the middle of butt and the toe.

Barrels with a series of holes or slots drilled near the muzzle. When a ported barrel is discharged, gasses moving violently down the barrel hit the forward edge of the holes and pull the gun forward off the shoulder, reducing felt recoil.

The platform from which all shooting fundamentals are executed. A position should be: Comfortable, balanced, relaxed and properly aligned with the target.

Informal shooting at any of a variety of inanimate targets. The most often practiced shooting sport in this country.

The ignition component of a cartridge, generally made up of a metallic fulminate or (currently) lead styphnate.

A small capsule of soft metal containing a detonating compound, press-fitted into the head of a cartridge. When the primer is struck by the firing pin, the small charge explodes, touching off the main powder charge inside the cartridge, launching the bullet or shot charge.

The test-firing of a gun with an extra-heavy load, at an official establishment, to verify the safety of a gun, which is then marked with formal stamps showing, among other things, the loads for which it is intended.

In a firearm the chemical composition that is ignited by the primer to generate gas. In air or pellet guns, compressed air or CO2.

A trade name for a blackpowder substitute, the only such safe substitute known at this time.

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