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


Port

An opening. The ejection port is the opening in the side of a semi-auto from which spent cases are ejected.

Crosshairs

The cross-shaped object seen in the center of a firearm scope. Its more-proper name is reticle.

Pre-Travel

Some triggers can be pulled slightly backwards before the shooter can feel any tension and before the hammer or striker begins to retract. Pre-travel is any movement of the trigger that begins before the trigger starts to engage.

Handspanner

German for Hand-Cocking or Cocker/De-Cocker. A type of action on a break-open gun or rifle where, in place of a traditional top tang safety, a somewhat more robust tab is fitted. Normally such a gun is carried in the field loaded, but with the action not cocked, an exceedingly safe condition. Then, when ready to fire, the shooter, instead of pushing a safety tab forward, pushes this larger tab forward, cocking the mainspring, making the gun ready to fire. Then, if the shot is not taken, he may simply slide this tab rearwards again, de-cocking the gun and returning it to the still-loaded, but very safe position.

Shot

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

Blown Pattern

A shotgun pattern with erratic shot distribution, generally caused by gas escaping past the wads and getting into the shot.

Wheel Gun

Slang term for a revolver.

Charging Handle

A device on a firearm which, when operated, results in the hammer or striker being cocked or moved to the ready position.

Heavy Machine Gun

A larger class of machine gun..

Battery

Most firearms do not have literal batteries. But a firearm is said to be in battery when the breech is fully closed and locked, ready to fire. When the breech is open or unlocked, the gun is out of battery and no attempt should be made to fire it. A semi-automatic is out of battery when the slide fails to come all the way forward again after the gun has fired, making it dangerous or impossible to fire the next round. 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.

Sight Alignment

The manner in which the sights are lined up properly in front of the shooter's eye, to form a straight path to the target.

Cold Range

A condition on a shooting range that is completely safe. Any firearms at the range are on the benches, unloaded with open actions and all people have stepped away from the firing line.

Dust Cover

A small hinged or sliding door covering the ejection port of a firearm to prevent detritus from clogging the works.

Kick

Slang for Recoil.

CCP

Abbreviation for Concealed Carry Permit.

Bore Axis

An imaginary line which runs right down the center of the handgun's barrel and out though the back end of the gun. A handgun may have a high bore axis, with the imaginary line running out into space well above the shooter's hand. Or it may have a low bore axis, with the imaginary line running either straight through the shooter's hand or just skimming the surface slightly above her hand. A high bore axis tends to create greater perceived recoil and more muzzle flip when firing the gun than does a low bore axis.

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.

Shot Size

The size of the pellets in a shotgun shell.

Railgun

A railgun is an electrically powered electromagnetic projectile launcher based on similar principles to the homopolar motor.
Using a magnetic field powered by electricity, a rail gun can accelerate a projectile up to 52,493 feet (16,000 meters) per second.
A railgun consists of two parallel metal rails (hence the name) connected to an electrical power supply. When a conductive projectile is inserted between the rails (at the end connected to the power supply), it completes the circuit. Electrons flow from the negative terminal of the power supply up the negative rail, across the projectile, and down the positive rail, back to the power supply.

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