Letter J

The Definition of Jam

Arsenal Exchange - Firearms Classifieds - Industry Directory

Jam

A malfunction which locks up the gun so badly that tools are required in order to fix it. Sometimes used to denote a simple malfunction, but many people make a distinction between a complete jam and a simple malfunction.


19 Other Firearms Definitions You Need To Know


FPS

Abbreviation for feet per second. A term used in expressing the velocity of a bullet.

Trajectory

The arc described by a projectile (or a load of shot) after it exits the muzzle of a firearm. Falling objects accelerate downwards at a rate of 32 feet per second, per second. The faster a projectile travels, the greater the distance it can cover in a given time before dropping too far. Hence, the higher the velocity of a bullet, the flatter the trajectory it will achieve.

WCF

Abbreviation for Winchester Centerfire.

Cheekpiece

A broad, flat, raised area on the side of a buttstock.

Safe

A firearm is said to be on safe when its safety is engaged and off safe when it is ready to fire.

Forend

One of the three major dismountable components of a break-open gun (the others being the barrel(s) and the action/buttstock) which secures the barrels to the receiver, often houses the ejector mechanism, and for some, provides a handle for the one's secondary hand.

Naked Bullet

A bullet not covered by a metal jacket or patch.

Explosive

Any substance (TNT, etc.) that, through chemical reaction, detonates or violently changes to gas with accompanying heat and pressure.

Monoblock Barrels

A method of building a pair of barrels where the entire breech end of both barrels and the lumps together are machined from one solid piece of steel. The barrel tubes are then fitted separately into this monoblock and the ribs attached. Often identifiable by a distinctive ring around the barrels about three inches in front of the breech end. The favored jointing method of the Beretta company. An incorrect euphemism for sleeved barrels.

Single Action

An action type that when the trigger is pulled, the only thing the trigger does is drop the hammer (or striker). This applies to both revolvers, semi-automatic and automatic guns. On a single action revolver, the gun must be manually cocked before it can be fired. With semi-automatic and automatic guns that are single action, the only thing the trigger does is drop the hammer, striker or firing pin onto the cartridge. Then the firearm is cocked again when from the recoil of the fired round. A firearm that the gun is cocked and the hammer drops when the trigger is pulled is a double action gun.

Doll's Head

A rib extension on a break-open gun, ending in a circular or semi-circular shape in plan (resembling the head of a doll), mating into a similarly-shaped recess in the top of the receiver, designed to resist the tendency of the barrels to pull away from the standing breech when firing. Because an action's centerpoint of flexing when firing is at the base of the standing breech, not at the hingepin, a passive doll's head extension makes an effective extra fastener, even without additional mechanical locks operated by the opening lever.

Direct Impingement

A type of gas operation for a firearm that directs gas from a fired cartridge directly to the bolt carrier or slide assembly to cycle the action.

HMR

Abbreviation for Hornady Magnum Rimfire.

Falling Block

A type of action used primarily for single shot rifles whereby some kind of lever actuates a breechblock, moving it downwards in a vertical recess to expose the chamber. May have visible or enclosed hammer. For any given barrel length, it allows a shorter overall rifle length compared to a bolt action because no space is taken up by the forward-and-back cycling of the bolt. Most of the better British makers produced them in limited numbers around the turn of the last century, the Farquharson being the most iconic. Perhaps the best-known falling block action today is the Ruger No.1.

Half grip

Round knob, semi pistol grip.

Magazine Follower

Same as Follower. A plate, mounted to the top of a spring, inside a magazine, over which cartridges may slide smoothly as they are guided into the chamber of a repeating firearm.

Half Cock

A middle position for an external hammer that effectively provides a safety function. With a firearm with non-rebounding hammers, when on half-cock, the firing pin will not rest on the firing-pin.

Clip

A clip IS NOT a magazine. A clip is used to load a magazine.
A clip is a simple, disposable narrow spring-lined channel-rail that is used to store multiple rounds of ammunition together as a unit, ready for insertion into the magazine of a repeating firearm. This speeds up the process of loading and reloading the firearm as several rounds can be loaded at once, rather than one round being loaded at a time. The term clip commonly refers to a firearm magazine, though this usage is absolutely completely totaly 100% incorrect. In the correct usage, a clip is used to feed a magazine or revolving cylinder, while a magazine or a belt is used to load cartridges into the chamber of a firearm. in which cartridges are supplied for military weapons. The shooter positions the clip vertically above the firearm's magazine, then pressing down with the thumb, slides the cartridges from the clip and down into the magazine.

Reset Point

The point of the trigger's return at which the gun's internal mechanisms are ready to fire another round.