TUMBLER

An English term that is sometimes used to denote a shotgun hammer. Also refers to an interior part of gun locks which contain notches that interact with the sear.

TUMBLING

1. The end-over-end rotation of an unstable projectile in flight. 2. A cleaning and polishing process, sometimes used in firearm part and ammunition manufacturing.

TUNNEL MOUNT

A telescope mount arrangement which has a hollowed-out base through which the iron sights may be seen and used.

TURNBOLT ACTION

A bolt action firearm on which it is necessary to rotate the bolt handle upwards for unlocking before it can be pulled to the rear. Similarly, it is necessary to rotate the bolt handle downward after closing to lock the firearm and enable the gun to be fired.

TWIN-SINGLE TRIGGER

A double trigger arrangement used on some double-barrel firearms, wherein one or both triggers will, with each pull, fire the barrels sequentially. They are non-selective.

TWIST

The distance required for one complete turn of rifling usually expressed as a ratio, e.g., 1 in 10 inches.

TWO PIECE STOCK

A stock consisting of two separate parts, the buttstock and forearm.

TRIP

A part of the mechanism of some firearms which is released by the action of the trigger.

TWO-PIECE MOUNT

A telescope mount having two separate base band ring assemblies.

TRIPLE BASE POWDER

A propellant composed of colloided nitrocellulose, nitroglycerine and nitroguanidine. Generally used in large caliber military ammunition.