Letter P

The Definition of Percussion Cap

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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.

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.


18 Other Firearms Definitions You Need To Know


Headspace Gauge

Plugs of hardened steel, precisely machined in relation to the standard dimensional specifications of a given cartridge, normally in sets of three: "GO", "No-Go" and "Field". By loading these plug-gauges into the chamber in succession, one can check that the action should close on the "Go" gauge. It should not close on the "No-Go" gauge, but might were enough force to be used. And, it absolutely should not close on the "Field" gauge.

Three Rules

The NRA teaches the Three Basic Rules of Safe Gun Handling. There are additional rules, but these are the three that if any two are followed, nobody will be hurt. However, obviously, all three should always be followed.

Rule One: ALWAYS keep the gun pointed in a safe direction.
Rule Two: ALWAYS keep your finger off the trigger until ready to shoot.
Rule Three: ALWAYS keep the gun unloaded until ready to use.
The NRA established these three rules in 1871. They were created to be easy to understand and remember, ensuring the highest possible level of firearm safety.
See also The Four Rules

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.

Front Sight

The front sight is placed at the muzzle end of the barrel. It is often (but not always) in the form of a dot or a blade. To attain a proper sight picture and shoot with the greatest degree of accuracy, the shooter's eye should be focused sharply upon the front sight while shooting, allowing both the rear sight and the target to blur somewhat.

Long Recoil

A semi-automatic pistol in which the barrel and breechblock are locked together for the full distance of rearward recoil travel, after which the barrel returns forward, while the breechblock is held back. After the barrel has fully returned, the breechblock is released to fly forward, chambering a fresh round in the process.

Light Double Action

A double-action semi-automatic firearm which is designed to have a much lighter trigger pull than is usual for a double action.

Machine Gun

A fully automatic firearm that rapidly fires multiple rifle-caliber shots with a single pull of the trigger.

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.

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.

Automatic

A type of firearm which, utilizing some of the recoil or some of the expanding-gas energy from the firing cartridge, cycles the action to eject the spent shell, to chamber a fresh one from a magazine, to cock the mainspring and to fire again. Such a firearm will fire continuously as long as the trigger is held back, until the magazine is empty. A machine gun. A firearm thus activated, but which shoots only one bullet with each separate pull of the trigger, while often erroneously referred to as "automatic" is properly termed Semi-Automatic.

Spotter

The spotter is a helper who gives the shooter guidance on how to hit a particular target. In some cases the spotter may just report the location of the bullet impact. In other cases they may judge the speed and direction of the wind, determine the range, and give the shooter the settings to be used on the sights.

Neck

The forward portion of a bottlenecked cartridge case. Also the portion of a rifle chamber in which the neck of the cartridge case rests.

Propellant

The substance which imparts movement to the projectile in a firearm. In a firearm, usually powder. In an airgun the propellant is air or Co2

Twilight Sight

A rifle front sight with a extra-large, folding bead. Typically, in addition to the normal fine bead (which allows for more precision) the larger bead, while at a cost of potential accuracy, is more readily acquired in marginal light. Also called a Gloaming sight

Crosshairs

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

Metallic Cartridge

A cartridge with a metallic case. (Early cartridge cases were made of linen, paper, etc.)

Jacket

A metal, usually copper, wrapped around a lead core to form a bullet.

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.