PYRAMID SIGHT

A type of front sight of triangular appearance. Also called Barleycorn Sight.

PRIMER SEATING

The insertion of a centerfire primer or battery cup in the head of a cartridge case or shotshell. Properly seated, it should be flush or below the face of the head.

PRIMER SETBACK

The condition when a primer, or battery cup primer assembly, moves partially out of its proper location in the primer pocket of a metallic cartridge or shotshell during firing.

PRIMER TUBE

A tube for holding primers in a handloading press.

PRIMING MIX/MIXTURE

A combination of explosive and/or pyrotechnic-type ingredients, which, when pressed into a cup or spun into the rim cavity of a rimfire shell, will ignite upon sufficient impact from a firing-pin and, in turn, initiate the propellant in a cartridge or shotshell.

PROJECTILE

An object propelled from a firearm by the force of rapidly burning gases or other means.

PROJECTILE ROTATION

The spinning motion that is imparted to a projectile due to engagement with the rifling in the barrel of a firearm, as it is driven down the barrel. The rate of rotation is dependent upon the rate of twist of the rifling and the velocity. The barrel twist (left or right) determines the direction of the rotation.

PROOF MARK

A stamp applied at or near the breech or other stressed component of a firearm after it has passed a proof test.