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


Round Gun

Slang term for a revolver.

Concealed

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

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.

Hood

Front sight hood. A hollow cylinder fitted to a rifle's front sight ramp, both to protect the delicate front sight bead from impact, and to shade it from oblique sunlight which could have the effect of altering the sight's apparent position.

Compensator

Also call a Muzzle Brake. A device attached to or made as part of a firearms barrel designed to reduce recoil or muzzle movement on firing. They generally increase muzzle blast.

Selective-Fire

A firearm's ability to be fired fully automatically, semi-automatically or, in some cases, in burst-fire mode at the option of the firer.

Snub-Nose

Slang word for short barreled revolver.

Grip Panels

The interchangeable surfaces that are installed on the part of the gun that you hold. Users change grip panels to improve the look or feel of the firearm, or to personalize it so that the gun is more suited to a different hand size. Some grip panels are chosen for function, while others are chosen for looks. Common grip-panel materials are wood, plastic, and rubber.

Overbore Ammunition

Small caliber bullets being used in large cases. E.g. .22 bullet in a .45 acp case.

Standing Breech

The face of the action of a break-open firearm which houses the firing pins and receives the direct recoil of the fired round.

Marksman

A person who can shoot up to the mechanical capability of their weapon.

Head

Head [of a Stock]. The forward end of a buttstock, where it meets the receiver and accepts the bulk of the gun's recoil when fired.

Long Colt

Although a misused term (even within the firearms industry), Long Colt is a designation for an ammunition cartrige developed by Colt mainly used for revolvers. The actual designation is Colt instead of Long Colt. The term Long Colt was originally coined to avoid confusion between the .45 Colt and .45 ACP cartridges

Negligent Discharge

The unplanned discharge of a firearm caused by a failure to observe the basic safety rules, not a mechanical failure of the gun.