Letter J

The Definition of JSP

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19 Other Firearms Definitions You Need To Know


Hammer Spur

The thumb-piece on the top rear of the hammer that enables it to be manually drawn back to full cock.

Center Of Mass

For self-defensive shooters, Center Of Mass (COM) represents the area of an attackers torso within which the most vital organs are likely to be disrupted by a gunshot. Shooting to COM is considered the most expedient way to stop an assailant from continuing threatening behavior.

Passive Safety

Any safety, internal or external, which functions apart from the shooter's conscious control. Grip safeties are one example of a passive external safety.

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.

Slamfire

A premature, unintended discharge of a firearm that occurs as a round is being loaded into the chamber.

SxS

Abbreviation for Side-By-Side.

Chamber Throat

This is the area in the barrel that is directly forward of the chamber, which tapers to the bore diameter.

Crisp Trigger

A trigger that breaks (to release the hammer) easy.

Antique Firearm

Defined according to Section 921 (a) (16), Title 18, U.S.C. as:

A. any firearm (including any firearm with matchlock, flintlock, percussion cap, or similar type of ignition system) manufactured in or before 1898; and
B. any replica of any firearm described in subparagraph (A) if such replica (i) is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition, or (ii) uses rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade.

Pattern

A shotgun term which refers to the manner in which the pellets spread out as they exit the gun. "The pattern" refers to the overall shape of the entire set. A tight pattern is one in which the pellets are closely grouped when they land on target. A loose pattern is one in which the pellets are widely spread.

Machine Pistol

A handgun-style fully automatic or burst-mode firearm.
A machine pistol is not the same thing as a Submachine Gun

Nipple

A small metal tube extending through the breech of a percussion firearm through which the flame passes from the percussion cap to fire the powder charge.

External Safety

A safety lever or button found on the outer surfaces of the firearm and is accessible to the user. Enabling the external safety should prevent accidental pulling of the trigger. However, the best safety is always you.

Island Rear Sight

A rear barrel sight base, more articulated than having the sight simply dovetailed into the barrel, but not requiring as much gunsmithing as having it mounted onto a proper quarter-rib.

Twist

The length, within a rifled barrel, required to accomplish one full rotation. 1:12 Twist, means a bullet passing down the bore would complete one revolution in twelve inches. 1:7 Twist, means a bullet passing down the bore would complete one revolution in seven inches, which makes it a tighter twist than 1:12. Different weights of bullet require appropriate rates of twist.

BG

Abbreviation for 'Bad Guy'

Curio and Relic

Firearms which are of special interest to collectors by reason of some quality other than is associated with firearms intended for sporting use or as offensive or defensive weapons. To be recognized as curios or relics, firearms must fall within one of the following categories:

  1. Firearms which were manufactured at least 50 years prior to the current date, but not including replicas thereof;
  2. Firearms which are certified by the curator of a municipal, State, or Federal museum which exhibits firearms to be curios or relics of museum interest; and
  3. Any other firearms which derive a substantial part of their monetary value from the fact that they are novel, rare, bizarre, or because of their association with some historical figure, period, or event. Proof of qualification of a particular firearm under this category may be established by evidence of present value and evidence that like firearms are not available except as collector's items, or that the value of like firearms available in ordinary channels is substantially less.
A special Curios or Relics license is available from the BATF, which allows collectors to buy eligible firearms in interstate commerce.

Silencer

Improper term for a device that cuts down on the noise a firearm makes when it is shot. The correct term is suppressor. Silencers only exist in the movies.

Drum Magazine

A type of firearms magazine that is cylindrical in shape, similar to a drum. Probably the most recognizable drum magazine is the magazine for a Thompson carbine rifle, also known as the Tommy Gun.

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