OAL: Abbreviation for Over All Length. See below.
OCTAGON BARREL: A barrel on a firearm that has eight flat sides instead of a round barrel. Abbreviated OB.
O'DWYER: Australian Inventor Mike O'Dwyer.
OGIVE: Refers to the nose shape of a bullet. The radius of the curve of a bullet nose. The curve of a bullet's forward portion.
OPEN SIGHT(S): A type of rear sight(s) characterized by an open topped notch. It is typically mounted on the rear portion of the barrel on rifles and shotguns or on the rear portion of a handgun's slide and used in conjunction with a blade type front sight. This is the standard type of sight on most handguns. When fitted to rifles and shotguns, it is imprecise and slow to acquire due to the distance between the sights and the distance of both the front and rear sights from the eye.
OVER ALL LENGTH: The total length of a cartridge, measured from bullet tip to base of case. In reloading the OAL is checked to ensure that the loaded cartridge is in compliance with the load standard. Abbreviated OAL.
OVERSHOOT: A term used in artillery to indicate a projectile impact beyond the designated target. Missing the target on the high side.
OVER UNDER: Refers to a doubled barreled firearm that has one barrel on top of the other. Also know as Over and Under. Abbreviated OU.
OVIS: Scientific genus for sheep. Genus Ovis Canadensis Anadems is the Rocky Mountain Bighorn, Ovis Canadensis Nelsoni is the Desert Bighorn sheep, Ovis Dalli Stonei is the Stone Sheep and Ovis Dalli Dalli is the Dall Sheep.
MAGAZINE: World bighorn sheep publication and conservation group
that accents "GRAND SLAM" and covers sheep (genus ovis) world
wide. (Grand Slam covers only the 4 species of North American sheep).