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


Centerfire (Center Fire)

A cartridge with its primer located in the center of the base of the case.

Percussion Cap

A small metal explosive-filled cup which is placed over the nipple of a percussion firearm. As the cap is struck by the hammer, it explodes and sends a flame through the flashhole in the nipple to the main powder charge.

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.

Shot

In shotgunning, multiple pellets contained in the shell and sent downrange when the shotgun is fired.

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.

Needle Gun

A needle gun is a bolt-action firearm (the first known type of bolt action rifle) that has a needle-like firing pin, which can pass through fully self-contained (paper) cartridge case to strike a percussion cap at the bullet base. The first experimental needle gun was designed by Jean Samuel Pauly, a Swiss gunsmith, in 1812. The first mass-produced needle gun was invented by the German gunsmith Johann Nicolaus von Dreyse, who, beginning in 1824, had conducted multiple experiments, and in 1836 produced the first viable breech loading gun model using a complete cartridge .

Snap Caps

Dummy cartridges with spring-loaded "primers" used to test the mechanical functioning of a firearm, particularly the trigger pulls, hammer-fall and ejector-timing of a break-open gun. It is not advisable to dry-fire a break-open gun on an empty chamber. Hardened steel parts can shatter without the soft brass primer to act as a shock absorber. Snap caps cushion the blow of the hammer and firing-pin when the use of a live cartridge would be impractical.

Barrel

A tube, usually metal, through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end at a high velocity. It is the tube through which the bullet or shot travels. The barrel serves the purpose of providing direction and velocity to the bullet.

Takedown

A firearm that can be separated into (at least) two subassemblies in order to make a shorter package than when put together, without tools. There is no specific requirement regarding how this disassembly must be accomplished; the mechanical design is up to the creativity of the maker. This arrangement allows for more convenient transportation of a firearm, but with rifles, where the action normally separates from the barrel, usually at a small sacrifice in accuracy. Takedown firearms can also be called take-apart firearms. Good examples of a takedown guns are the Henry AR-7 Survival Rifle, the Ruger 10/22 Takedown or the TNW Aero.

Short-Stroking

On a pump-action firearm, being too gentle with the fore-end and either not pulling it all the way back at the beginning of the stroke, or not shoving it all the way forward at the end of the stroke. Which may result in the old case or shell failing to eject and a misfeeds, or the gun will not fire when the trigger is pulled. The term is used most often to refer to pump-action shotguns, but it is possible to similarly short-stroke any type of firearm which requires the user to manually cycle the action (lever action rifles, for example).

Matched Pair

Two firearms that are manufactured identical in every way and are sequentially serial numbered and are sold as a set. The most common type of matched pair guns are cowboy style revolvers for a couple of reasons, both guns will feel exactly the same in the hands and they make the set more collectable.

Failure To Fire

Any malfunction that results in no shot fired when the trigger is pulled. Commonly caused by a failure to feed, bad ammunition or a broken firing pin.

Practical Shooting

A shooting sport that simulates the use of a small arm in its intended role either as a tool for hunting or personal defense. True practical shooting limits the small arms, ammunition, and accessories used to those items that would actually be used in the role simulated.

Sling

A strap, usually of leather or sturdy webbing, fitted to the fore and aft (usually) of a rifle as an aid to carrying over the shoulder and as an aid to holding the rifle steadily while aiming.

Suppressor

Incorrectoly sometimes referred to as a silencer, it is used to reduce the sound of a firearm's discharge. They do not actually silence most firearms but rather lower the intensity of the muzzle blast and change the sound characteristics (works similarly to an automotive muffler by disrupting and spreading out the sound waves). The possession, use, and transportation of silencers have been tightly controlled under federal law since 1934. Any device which reduces the sound of discharge by more than 2 dB is considered by the BATF to be a suppressor.

Wheel-Lock

An early firearm mechanism in which a wheel with serrated edges is wound against the tension of a strong spring and spins against a piece of iron pyrite, sending a shower of sparks into the pan to ignite the charge.

Garniture

A deluxe set of several different associated weapons, being any combination of rifle, shotgun, various handguns, and possibly a knife or two, cased together with appropriate cleaning and loading tools.

Frame

The common part of a handgun to which the action, barrel and grip are connected.

Deterrent

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