Letter O - Firearms Dictionary of Gun Terms, Slang and Abbreviations

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Obturation

The process of a bullet expanding under pressure to fit the bore of the firearm, or a cartridge case expanding under pressure to seal the chamber.

OFF

Oregon Firearms Federation. OFF is a Pro-Gun rights group based in Oregon and was founded in 1998.

Off Hand

To shoot while standing and without bracing against anything. Sometimes it can also mean to shoot with your non-dominant hand.

Ogive

A type of curve represented by the curved section of a bullet between its bearing surface and its tip.

A type of firearm in which the action is in the open position and the chamber empty prior to firing. When the trigger is pressed the bolt moves forward, chambering a cartridge and firing it and returning to the open position. When firing is stopped the bolt remains open and the chamber empty.

Open Frame

Refers to a revolver frame that has no top-strap over the cylinder.

Open Sights

A common type of iron sights in which the rear sight is an open-topped U or a V or a square-notch shape and with a blade type front sight, in contrast to the closed circle commonly found in aperture sights.

Open Tip Match

A rifle projectile made with the tip of the bullet open as a means of increasing accuracy as compared to standard military bullets that are made with a closed tip and an open base. The are not designed to expand like a hollow point bullet but may fragment.

Optical Sight

Usually a telescopic firearm sight.

Oregunian

A person living in the State of Oregon that is a firm supporter of the Second Amendment (plus the other nine Bill of Rights amendments) and generally will also be a firearms enthusiast.

In other words "A Gun Loving Red Blooded American that Hails from The State of Oregon"

OTM

Abbreviation for Open Tip Match.

Out of Battery

A semi-automatic is said to be out of battery when the slide fails to come all the way forward again after the gun has fired. This condition can be created by a misfeed, a dirty gun, weak springs, the shooter's thumbs brushing against the slide, riding the slide, or any of several other causes.

Over Travel

If the trigger is able to continue moving to the rear after the shot has fired, the trigger is said to over-travel.

Over-Under

Can also be spelled Over/Under, OverUnder or Over and Under. A firearm (most commonly a shotgun) with two barrels that are vertically aligned with each other, one on top of the other.

Overbore Ammunition

Small caliber bullets being used in large cases. E.g. .22 bullet in a .45 acp case.

Overbore Capacity

Is that combination of caliber, barrel length, bullet weight, and case volume which does not allow the complete burning of the charge of ballistically correct powder within the volume of case and barrel.

Overshoot

A term used in artillery to indicate a projectile impact beyond the designated target.

3 Other Firearms Definitions You Need To Know

Accidental Discharge

An unexpected and undesirable discharge of a firearm caused by circumstances beyond the control of the participant(s) such as a mechanical failure or parts breakage. There are very, very few firearms related "accidents" and if the "Three Rules" are followed there will hopefully be no injury. Accidental Discharge should not be confused with "Negligent Discharge".

Bersa

A firearms manufacturer located in the city of Ramos Mejia in Argentina. The company was founded in the mid-1950s by Italian immigrants Benso Bonadimani, Ercole Montini and Savino Caselli, all of them mechanical engineers with experience working for Beretta. Bersa is most famous for their Bersa Thunder .380 pistols and the Thunder Ultra Compact Pro Pistols (available in 9mm, .40 S&W and .45 acp). The full size Thunder combat (Thunder 9) pistol is the standard sidearm of the Argentina Armed Forces, Buenos Aires Provincial Police and several other law enforcement agencies in South America. The company is well known among firearm enthusiasts for producing high quality guns at reasonable prices and it spends little money on advertisement. Lifetime warranty coverage is provided to the original owners. They are strong and well built, nicely engineered, accurate, visually appealing and very reliable.

Crane

A swing-out arm on a revolver, to which the cylinder is mounted when opened facilitates loading and cleaning.