Letter: O

Handle of semi or full automatic firearm used to cycle firearm without firing. Also called Charging Handle, Cocking Handle, Cocking Knob.

The distance after a particular event occurs in the normal operation of the firearm, e.g. additional rearward motion of the trigger after sear or hammer release.

Various designs of separators, made of various materials and used between the propellant powder and the shot pellets.

The point where the powder charge of a particular burning rate of propellant exceeds the capacity of a barrel of specific caliber and length to convert the propellant gas pressure to velocity.

A shotgun barrel bore diameter greater than the SAAMI maximum for that gauge. Also called a Baker Bore.

1. Firearm: The dimension measured parallel to the axis of the bore from the muzzle to a line at right angles to the axis and tangent to the rearmost point of the butt-plate or grip.

2. Ammunition: The greatest dimension of a loaded cartridge, i.e., from face of the head to the tip of the bullet for centerfire or rimfire or to the crimp for shotshells or blanks (not to be confused with the uncrimped length in a shotshell.)

Firearms with two barrels placed one above the other.

A lead bullet lubricated on the surface not covered by the cartridge case.

The condition of the breeching mechanism of a firearm not being completely locked or completely closed.

When a bullet exits from the barrel of a firearm, the location of the center of the bore at that specific point in time is called the origin of the trajectory.