Glossary of Firearms Terms - U

U

• upset forging: A process that increases the diameter of a workpiece by compressing its length.

• underlug: 1. 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. 2. The metal shroud underneath the barrel of a revolver that surrounds and protects the extractor rod. The two types of underlugs include half-lug, meaning the shroud doesn't run the entire length of the barrel but instead is only as long as the extractor rod, and full-lug, meaning the shroud runs the full length of the barrel.

• underwater firearm: a firearm specially designed for use underwater.