Firearms Definitions You Need To Know

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Terminal Ballistics

A sub-field of ballistics, is the study of the behavior of a projectile when it hits its target.

Dum-Dum

A bullet designed to expand on impact, increasing in diameter to limit penetration and/or produce a larger diameter wound. The two typical designs are the hollow point bullet and the soft point bullet. Expanding bullets were given the name Dum-dum, or dumdum, after an early British example produced in the Dum Dum Arsenal, near Calcutta, India by Captain Neville Bertie-Clay in the the mid-1870s. Modern sef-defensive, JHP (Jacketed Hollow Point), ammunition are based on the original dum-dum ammunition design and principles.

Ejection Rod

The sliding metal dowel located at the muzzle end of a revolver cylinder. After firing, the shooter opens the cylinder and depresses the front end of the ejection rod, which forces the empty cases out of the cylinder.

M1911

The official US military designation for the Colt .45 semiautomatic pistol adopted by the US in 1911. The gun was designed by John Moses Browning, and produced by Colt. During trials, the Browning-Colt design beat out several competing designs, including one from Savage and a .45 caliber version of the German Parabellum ("Luger"). The M1911 saw its first combat in the Philippines and then in World War I. Early use showed that it could be improved and in 1921 the M1911A1 was introduced, which featured a few changes like a reocontoured frame, shorter trigger, and a rounded backstrap. The M1911A1 remained the standard US military handgun until it was replaced in the 1980's by the Beretta M9. However, it remains very popular with civilian shooters in the US, and has been modified extensively to update it to conform to more modern theories of handgun usage.

Gain Twist

A form of rifling where the helical angle (pitch) sharpens progressively down the bore in the interest of maximizing the bullets ultimate rotational speed by initiating it slowly.

Carry

Slang for a gun or the action of carrying a gun concealed, e.g "The Bersa Thunder .380 is a fantastic gun for carrying" or "Do you carry?".

Sniper Rifle

A specialized, highly accurate rifle, fitted with an optical sight used by military snipers to engage personnel and hard targets at long range.

Stance

How the shooter positions her body while shooting. The three most widely used handgun stances are Weaver, Isosceles and Chapman stance.

NFA

National Firearms Act of 1934. Enacted on June 26, 1934, currently codified as amended as I.R.C. ch. 53, is an Act of Congress in the United States that, in general, imposes a statutory excise tax on the manufacture and transfer of certain firearms and mandates the registration of those firearms. The Act was passed shortly after the repeal of Prohibition. The NFA is also referred to as Title II of the Federal firearms laws.
The NFA includes:

  • Requires the registration of all fully automatic firearms.
  • Requires the registration of all "sawed off" rifles and shotguns.
  • Requires the registration of firearm silencers.
  • Imposes a $200 transfer tax on the above items.

Live Fire Exercise

Any exercise in which a realistic scenario for the use of specific equipment is simulated. In the popular lexicon this is applied primarily to tests of weapons or weapon systems that are associated with the various branches of a nation's armed forces, although the term can be applied to the civilian arena as well.

Port

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

Underhammer

A type of lock in which the hammer pivots in a vertical arc, striking the nipple on the underside of the barrel. Since the nipple's flash channel goes straight into the powder at the breech end of the barrel, ignition time is very fast. For this reason, and because it gets the hammer out of the way, underhammer locks are commonly used on muzzleloading benchrest rifles which are used for target shooting, and where accuracy is the goal.

Throat Erosion

The wearing of the portion of the barrel where the gas pressure and heat is highest as the projectile leaves the chamber. The greater the chamber pressure the more rapid throat erosion occurs which is compounded by rapid firing which heats and weakens the steel.

Adjustable Trigger

A trigger that can be easily adjusted by the user. Adjustable triggers are common on specialized target-shooting firearms.

Cartridge Overall Length

This is the maximum overall length the cartridge can be (and is expected to be) in order to function properly in magazines and the mag well of a bolt action rifle.

Soft Point

A metal jacketed bullet design in which the nose of the core of the bullet is exposed to ensure the expansion of the bullet upon impact. Often abbreviated "JSP" or "SP." They tend to expand more slowly than a Hollow Point bullet and are used where deeper penetration and expansion are needed.

Drift

The departure of a bullet or shot charge from the normal line of flight. This can be caused by wind or the unbalanced spinning of the bullet.

Grain

A unit of weight widely used to express the weight of bullets and of powder charges. Equal to 1/7000 pound.

Nose

The point of a projectile.

SMLE

Abbreviation for Short Magazine Lee Enfield. The standard British Army rifle from around 1895 to 1957.

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