Letter O

The Definition of OTM

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19 Other Firearms Definitions You Need To Know


A metal plate on which the firing mechanism is mounted on percussion and earlier firearms.

Tangent Sight

A style of rear sight, typically used on rifles for either slow-moving bullets or for long ranges, whereby a ladder may be raised from flush with the barrel to a vertical position, and which incorporates a sliding crossbar which may be moved vertically in order to achieve significant elevation.

Disc-Set Strikers

Circular steel fittings, about 1/2 inch in diameter, screwed into the breech face of a gun and through which the firing pins pass. Firing pin bushings allow the convenient replacement of broken firing pins. They also allow the renewal of an older gun where, over the decades, leakage of high-pressure gas from corrosive primers has eroded the breech face around the firing pins; and replacing these bushings with new ones, slightly oversized can compensate for a situation where proper headspace has been compromised.

Isosceles Stance

There are two basic variants of the Isosceles stance, the Traditional Isosceles and Modern Isosceles stance. In both Isosceles stances, the feet parallel pointing toward the target and are roughly shoulder width apart. Both arms are stretched almost equally forward with the gun centered forward, creating the triangular shape which gives the stance its name.

Forcing Cone

In a shotgun barrel, A tapered area a few inches from the breech end, providing a transition between the chamber (approximately the diameter of the outside of a shotgun shell) to the bore proper (approximately the diameter of the inside of a shotgun shell). The forcing cone provides the transition between the exterior and the interior diameters of the cartridge. Older shotguns usually have more abrupt forcing cones suitable for then-current thick-walled paper shells with fibre wads. Newer shotguns usually have more gradual, longer forcing cones suitable for thinner modern plastic shells with obturating plastic shot-cup wads.

Slide Lock

A slang term for slide catch.


Abbreviation for Arsenal Exchange or ArsenalExchange.com. Example in a sentence is "Have you seen the latest postings on AE?
AE is also the abreviation for Action Express. .50 Action Express (.50 AE) is a large caliber handgun cartridge. It was developed in 1988 by Evan Whildin of Action Arms.


A unit of weight widely used to express the weight of bullets and of powder charges. Equal to 1/7000 pound.


A firearm designed to fire a single cartridge, eject the empty case and reload the chamber each time the trigger is pulled. It uses the energy from the fired shot to eject the empty case and feed the next round into the chamber.

Double-Set Trigger

Usually only found on black powder muzzle loading rifles and pistols, pulling the rear (set) trigger converts the front (main) trigger to a light, hair trigger (too light and sensitive to be carried safely in the field). While the front trigger is always at the ready, if one has the time, using the set trigger feature may allow for a more accurate long-distance shot. Operates using its own miniature firing mechanism (sear, spring and hammer) when cocked, to multiply the force of a pull on the main trigger.

Flashbang (holster)

A flashbang holster is a type of holster for women that allows the firearm to sit horizontally tucked under the bra band. As the gun is pulled straight down, the clamshell opens up and permits the wearer to draw. It is named a flashbang because the wearer hash to pull up their shirt (flash) to draw the gun out of the holster, then shoot (bang). These holsters have become very popular with women that conceal carry since the firearms is neatly hidden under the breast line in clothing and does not require the wearer to stay latched onto a purse or have to deal with the inconviences that come with inside the waist band carry

Scope Blocks

A pair of small dovetailed steel bases, screwed usually one to the barrel and one to the front receiver ring of a rifle, to accept mounts for target scopes such as the Unertl where the scope is allowed to move forward in the rings under the recoil of the rifle and which typically carry the windage and elevation adjustments in the mount.


Abbreviation for 'Back Up Gun'


A gun holder that may be strapped to a human body, or affixed to the inside of a pack or bag, or dropped into a pocket. A holster serves to protect the gun's mechanisms and finish, to provide security by covering the trigger so it cannot be pulled inadvertently, and to present the grip of the gun at a constant angle for easy access. Some holsters also serve to obscure the outline of the gun so it may be more easily concealed. Typically made from leather or in plastic.


Italian for "short." Seen as part of a cartridge designation. On some Italian manufactured guns that use .380 ACP, the designated caliber is 9mm Corto (9mm Short), which is also the same as the German 9mm Kurtz

Lock Time

The interval of time between trigger release and the detonation of the primer. Generally, the faster the lock time the better, because this makes it easier to shoot accurately.

Reactive Targets

Targets that do something when you hit them, such as fall over, burst, send up smoke, or make a noise.


Originally used to describe the spherical projectile used in black powder firearms, now also used to refer to a fully jacketed bullet of cylindrical profile capped with a round nose


Abbreviation for Concealed Handgun License.