Letter: O

A mount for a telescopic sight that consists of a one piece base as opposed to a two piece base.

The treatment of a cartridge to minimize the entry of oil or water.

A shallow indentation in a cartridge case, generally caused by excessive oil:
a) present in dies during case manufacture
b) in re-sizing dies during handloading operations
c) in a chamber during firing

The curved forward part of a bullet.

The curved portion of a bullet forward of the bearing surface.

A curved buttstock for use by a shooter who wishes to use the left eye when shooting right handed or vice versa. Also known as a Cross-Over Stock.

A mount for telescopes or iron sights affixed to the gun in such a manner, that the line of sight is to the side and above the receiver or barrel.