Letter U Firearms Glossary

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Underbolts

A sliding bar, running longitudinally through the watertable of a break-open side-by-side gun's action, with openings through which the lumps of the barrels pass when the gun is closed. Under spring tension, this bar moves forward when the opening control is released and its two locking surfaces engage complementary slots (bites) in the rear of the two barrel lumps. Originally operated by a hinged tab in front of the trigger guard. Now invariably operated by a cam from Scott's [toplever] spindle. Most modern side-by-side guns lock closed in this manner.

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.

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.

Underwater Firearm

A firearm specially designed for use underwater.

Upset Forging

A process that increases the diameter of a workpiece by compressing its length.


14 Other Firearms Definitions You Need To Know


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.

Slide Bite

A phenomenon which is often grouped with hammer bite. In this case the web of the shooting hand is cut or abraded by the rearward motion of the semi-automatic pistol's slide, not by the gun's hammer. This most often occurs with small pistols like the Walther PPK and Walther TPH that have an abbreviated grip tang. This problem is exacerbated by the sharp machining found on many firearms.

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.

Stutzen

German for a short rifle or carbine.

Knuckle

The curved, forward end of the bar of a break-open firearm's action, about which the mounted forend iron revolves downward. This area should be kept lightly greased to avoid galling the bearing surfaces.

Adjustable Stock

The stock is the wooden, polymer, or metal handle of a long gun that extends from the trigger back to where the gun is braced against the shoulder. An adjustable stock is one that can be easily lengthened or shortened to fit shooters of different sizes.

BUG

Abbreviation for 'Back Up Gun'

Slug

More correctly a "rifled slug" or "shotgun slug." An individual cylindrical projectile designed to be discharged from a shotgun. The term is often incorrectly used to mean a Bullet.

Light Double Action

A double-action semi-automatic firearm which is designed to have a much lighter trigger pull than is usual for a double action.

Long Rifle

Typically used in the .22 caliber cartridge designation .22 Long Rifle, which is abbreviated .22LR.

Lands

In the rifling of a bore, the uncut portions of the barrel's inner surface left after the rifling grooves have been cut into the metal. In other words, the raised portion of rifling.

Island Rear Sight

A rear barrel sight base, more articulated than having the sight simply dovetailed into the barrel, but not requiring as much gunsmithing as having it mounted onto a proper quarter-rib.

Cylinder

The part of a revolver that holds cartridges in separate chambers radially around a central hingepin. The cylinder revolves as the handgun is cocked, , either to the left or to the right depending on the gun maker's design, bringing each successive cartridge into position, and locked into alignment with the barrel for firing.

Bedding

That part of the stock on a rifle or shotgun into which the barrel fits.

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