Letter U

The Definition of Underhammer

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Underhammer

A type of lock in which the hammer pivots in a vertical arc, striking the nipple on the underside of the barrel. Since the nipple's flash channel goes straight into the powder at the breech end of the barrel, ignition time is very fast. For this reason, and because it gets the hammer out of the way, underhammer locks are commonly used on muzzleloading benchrest rifles which are used for target shooting, and where accuracy is the goal.


19 Other Firearms Definitions You Need To Know


Powder Charge

The amount of propellant powder that is suitable for specific cartridge-bullet combination, or in the case of shotshells, for a specific weight of shot and wad column.

Manual Safety

A safety which the shooter must deliberately disengage in order to fire the gun. The most common form of safety mechanism is a switch that, when set to the "safe" position, prevents a pull of the trigger from firing the firearm.

Ghost-Ring Sight

A type of aperture rear sight with a large opening and a thin rim that seems to fade out when the shooter looks through it. Sometimes installed on rifles and shotguns intended for home defense or police use.

Center Hold

A sight picture of when the center of the target is half covered by the front sight when the sights are properly aligned. Also see six o'clock hold and cover hold.

Battery

Most firearms do not have literal batteries. But a firearm is said to be in battery when the breech is fully closed and locked, ready to fire. When the breech is open or unlocked, the gun is out of battery and no attempt should be made to fire it. A semi-automatic is out of battery when the slide fails to come all the way forward again after the gun has fired, making it dangerous or impossible to fire the next round. This condition can be created by a misfeed, a dirty gun, weak springs, the shooter's thumbs brushing against the slide, riding the slide, or any of several other causes.

Hair Trigger

A trigger that breaks from an extremely light touch.

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.

Matchlock

A black powder muzzleloading firearm action which relies upon a serpentine or S-shaped piece of metal to hold a smoldering match. By pressing the lower end of the serpentine, the upper end holding the burning match contacts the priming powder in the pan.

Brass

The term used for the casing on modern rifle and pistol ammunition. It is usually made out of brass but can also be aluminum or steel. The casing on a shotgun shell is usually refered to as a hull

Magna

Smith & Wesson term for a revolver grip design introduced in the 1930s where the top of the grip extends higher than it had in earlier configurations, to provide a more comfortable hold.

Charging Handle

A device on a firearm which, when operated, results in the hammer or striker being cocked or moved to the ready position.

Open Bolt

A type of firearm in which the action is in the open position and the chamber empty prior to firing. When the trigger is pressed the bolt moves forward, chambering a cartridge and firing it and returning to the open position. When firing is stopped the bolt remains open and the chamber empty.

Ammo

Slang word abreviation for Ammunition.

Tracer

A type of ammunition that utilizes a projectile or projectiles that contain a compound in its base that burns during its flight to provide a visual reference of the projectile's trajectory.

Breechloader

A firearm loaded through the breech.

Trace

Visible disturbance in the air by a bullet. Typically this takes the form of image distortion that persists for a fraction of a second in the shape of an inverted V similar to that of a boat wake.

LFX

Abbreviation for Live Fire Exercise

Monoblock Barrels

A method of building a pair of barrels where the entire breech end of both barrels and the lumps together are machined from one solid piece of steel. The barrel tubes are then fitted separately into this monoblock and the ribs attached. Often identifiable by a distinctive ring around the barrels about three inches in front of the breech end. The favored jointing method of the Beretta company. An incorrect euphemism for sleeved barrels.