Letter S

The Definition of Sectional Density

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Sectional Density

The relationship between a bullet's weight and its diameter. A long bullet, such as the original 7.62x54R loading for the Mosin Nagant 91/30, will have a high sectional density and consequently greater penetration than a shorter bullet of similar construction. A shorter bullet with less sectional density will have relatively less penetration, but greater knockdown power.


19 Other Firearms Definitions You Need To Know


Pinfire

An early form of complete, self-contained cartridge. It included bullet, powder and ignition primer, all in one package. The primer was located towards the base of the cartridge, but completely internally. The pin, shaped like a little finishing nail, pointed on the inside end and resting on the internal primer, projected radially about a quarter-inch to the outside of the base of the cartridge. When loaded, a pinfire gun showed the tips of the pins exposed through small slots in the tops of the breech faces of the barrels. To fire, hammers fell on the pins, driving them (through the wall of the cartridge) into the internal primer.

Clicks

A unit of adjustment for a sight.

Sectional Density

The relationship between a bullet's weight and its diameter. A long bullet, such as the original 7.62x54R loading for the Mosin Nagant 91/30, will have a high sectional density and consequently greater penetration than a shorter bullet of similar construction. A shorter bullet with less sectional density will have relatively less penetration, but greater knockdown power.

Closed Bolt Firing System

A type of firearm in which the action is closed, with a cartridge in the chamber prior to firing. When the trigger is pressed the cartridge is fired, and the action cycles loading another cartridge into chamber and when firing is stopped the bolt remains closed and the chamber remains loaded.

Magazine Well

The opening in the bottom of the gun into which a box magazine is fed. On a semi-auto handgun, the magazine well is at the base of the grip; on a rifle, it is usually placed in front of the trigger guard.

High Brass

By convention, powerfully loaded shotgun cartridges for hunting are generally manufactured with relatively longer brass end-caps than lower powered cartridges intended for target shooting. While different-sized brass bases are of virtually no consequence to the strength of the shell in relation to the steel breech of the gun itself, they do help the shooter identify the relative power of cartridges at a glance.

Grip

The portion of the stock (on a rifle) or frame (on a pistol) gripped by the trigger hand.

Short Trigger

A trigger that doesn't have to travel very far before it reaches the break. In a 1911 semi-auto pistol, a short trigger is a different part than a long trigger, and (in addition to providing less motion) it features a shorter reach which may be of benefit to a small-handed shooter.

Misfire

The condition of a cartridge not firing when an attempt to fire it is made. It can be caused by either a defective cartridge or a defective firearm. The term is frequently misused to indicate a Negligent Discharge of a firearm.

Muzzle Brake

An attachment to or integral part of the barrel that redirects some of the pressurized gas that propelled the bullet out the muzzle to the sides and possibly rearwards from the direction of the bullet travel. This reduces the recoil of the firearm.

Bolt Thrust

The amount of rearward force exerted by the propellant gases on the bolt or breech of a firearm action or breech when a projectile is fired. The applied force has both magnitude and direction, making it a vector quantity.

Lug

Any piece that projects from a firearm for the purpose of attaching something to it. For example barrel lugs are used to attach a break-action shotgun barrel to the action itself. If the firearm is a revolver, the term may also refer to a protrusion under the barrel that adds weight, thereby stabilizing the gun during aiming, mitigating recoil, and reducing muzzle flip. A full lug extends all the way to the muzzle, while a half lug extends only partially down the barrel. On a swing-out-cylinder revolver, the lug is slotted to accommodate the ejector rod.

Pellet Gun

An air gun that shoots a skirted pellet.

Point Blank Shooting

Shooting a target at a very very close range.

Revolver

A repeating firearm in which the ammunition is held in a multi-chambered cylinder, which is rotated to bring each chamber in line with the barrel. Most revolvers are handguns, although shoulder-fired arms have been made using this sort of mechanism.

DAO

Abbreviation for Double Action Only. Is a type of firearm in which the firing mechanism cannot be cocked in a single-action stage. Firing always occurs as a double-action sequence where pulling the trigger both cocks and then fires the gun.

Wad

A felt, paper, cardboard or plastic disk that is used in a shotshell. Also in muzzle loading, a piece of cloth used to seal the bullet in the barrel. It's purpose and function is the same as a shotgun wad.

Open Bolt

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.

Deterrent

A material added to an explosive to slow its burning rate.
Something that will prevent or hinder something from happening.