Letter U

The Definition of Underlug

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Underlug

The locking lugs on a break-action firearm that extend from the bottom of the barrels under the chamber(s) and connect into the receiver bottom.


19 Other Firearms Definitions You Need To Know


Repeater

A type of firearm capable of discharging multiple individual shots in sequence, fed from a magazine, via the operation a lever, bolt, slide or some other form of manual operation.

Penetration

The distance travelled by a projectile from the point where it strikes the target to the point where it stops.

Short Recoil

A semi-automatic pistol in which the barrel and breechblock are locked together for only a short distance of rearward recoil travel, at which point the two are uncoupled, the barrel is stopped and the breechblock continues rearward, extracting the spent casing from the chamber. Upon returning forward, the breechblock chambers a fresh round and forces the barrel back into its forward position. Most modern recoil operated semi-automatic pistols use short recoil.

LC

Abbreviation for Long Colt

Concealed

Hidden from view. A handgun is concealed when it is carried in such a manner that is unseen.

Toplever

A lever on a break-open gun mounted to the top of the receiver which, when pushed with the thumb (normally) to the right, operates (usually) a Scott Spindle, which in turn withdraws (usually) a Purdey Underbolt from the bites in the lumps of the barrels, allowing them to hinge downwards and the gun to open.

Casing

Also known as a Case. The envelope (container) of a cartridge. For rifles and handguns it is usually of brass or other metal; for shotguns it is usually of paper or plastic with a metal head and is more often called a "shell."

Reflector Sight

A generally non-magnifying optical device that has an optically collimated reticle, allowing the user to look through a partially reflecting glass element and see a parallax free cross hair or other projected aiming point superimposed on the field of view. Invented in 1900 but not generally used on firearms until reliably illuminated versions were invented in the late 1970s (usually referred to by the abbreviation "reflex sight").

Drilling

A three-barrel gun. Typically it has two shotgun barrels side by side on the top, with a third rifle barrel underneath. This provides a very versatile firearm capable of taking winged animals as well as big game. It also is useful in jurisdictions where a person is only allowed to own a single firearm.

Racking the Slide

Pulling the slide back to its rearmost position, and then letting it go forward under its own spring tension. Racking the slide loads the chamber and prepares the gun to fire in a semi-automatic handgun.

Martini

A hammerless single shot action type whereby a breech-block, hinged at the upper rear, operated by an underlever, tilts downward to expose the chamber.

Railgun

A railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor.
Using a magnetic field powered by electricity, a rail gun can accelerate a projectile up to 52,493 feet (16,000 meters) per second.
A railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (at the end connected to the power supply), it completes the circuit. Electrons flow from the negative terminal of the power supply up the negative rail, across the projectile, and down the positive rail, back to the power supply.

Center Of Mass

For self-defensive shooters, Center Of Mass (COM) represents the area of an attackers torso within which the most vital organs are likely to be disrupted by a gunshot. Shooting to COM is considered the most expedient way to stop an assailant from continuing threatening behavior.

Pistol

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.

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.

Multi-Barreled

A gun with more than one barrel, the most common being the double-barreled shotgun.

Safety

A device, incorporated into the design of most firearms actions that, when engaged, should prevent the discharge of the firearm. Some safeties are more positive than others. A safety device is not a perfect substitute for the general principles of responsible gun handling. Never point a gun in a direction you do not intend to shoot

Speed Loader

A device used to load magazines or revolver cylinders quicker than by hand.

Curio and Relic

Firearms which are of special interest to collectors by reason of some quality other than is associated with firearms intended for sporting use or as offensive or defensive weapons. To be recognized as curios or relics, firearms must fall within one of the following categories:

  1. Firearms which were manufactured at least 50 years prior to the current date, but not including replicas thereof;
  2. Firearms which are certified by the curator of a municipal, State, or Federal museum which exhibits firearms to be curios or relics of museum interest; and
  3. Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event. Proof of qualification of a particular firearm under this category may be established by evidence of present value and evidence that like firearms are not available except as collector's items, or that the value of like firearms available in ordinary channels is substantially less.
A special Curios or Relics license is available from the BATF, which allows collectors to buy eligible firearms in interstate commerce.