Firearms Glossary M - Z
M Machine Gun - A firing mode that fires more than one round per action (trigger pull) by the shooter. Can include burst mode as well as full automatic.
Machine Pistol - A handgun capable of fully automatic or burst-mode operation.
Magazine - An ammunition storage and feeding device within or attached to a repeating firearm. Different than a clip.
Magazine well – The opening in a firearm into which a magazine is placed.
Malfunction – Any type of unexpected or undesired operation by a firearm, which may include misfeeds, failures to fire, eject, or feed, parts breakages, and other stoppages.
Match Grade - Firearm parts and ammunition that are suitable for a competitive match.
Minute of Angle (MOA) – A unit of angle that is equal to 1/60 of one degree. Approximately one inch at 100 yards. See
"Just What the Heck is MOA and Why Should I Care?"Moon Clip – A flat, circular clip to hold cartridges for loading into a revolver's cylinder. Also available as partial moon clips (half-moon or third-moon) clips that hold fewer rounds to facilitate partial reloads.
Mouse Gun – A small handgun which fires a diminutive cartridge.
Muzzle - The "business end" of the barrel from which a projectile exits.
Muzzle Brake - A device fitted to the muzzle of a firearm to redirect gases with the effect of countering both recoil of the gun and unwanted rising of the barrel during rapid fire.
Muzzle Energy - The kinetic energy of a projectile as it is expelled from the muzzle of a firearm.
Muzzle Velocity - The speed at which a projectile leaves the muzzle of a firearm.
N National Firearms Act (NFA, NFA 34) – The set of federal regulations governing sale and possession of certain types of firearms and accessories such as machine guns, short barreled shotguns and rifles, and silencers. The NFA imposes a $200 transfer or making tax on most of these items ($5 on certain items) and requires registration of such items into the NFRTR.
National Firearm Registration and Transfer Record (NFRTR) - The central registry of all NFA firearms in the U.S. which are not in the possession or under the control of the U.S. Government.
National Rifle Association of America (NRA) - An organization that lists its goals as the protection of the Second Amendment of the United States Bill of Rights and the promotion of firearm ownership rights as well as marksmanship, firearm safety, and the protection of hunting and self-defense in the United States.
Negligent Discharge (ND) – The unplanned and unexpected discharge of a firearm caused by the operator through unsafe firearm handling practices. Although some refer to them as accidental discharges, nearly all unexpected discharges fall into this category (through failure to properly ensure that a firearm is empty, not ensuring that a safety device is enabled, placing a finger or other object into the trigger guard when not prepared to fire, and so on).
Night Sights - A type of sights with higher visibility for use in low light conditions.
O Off-Hand - Shooting unsupported (without a rest or while standing and not braced against an object).
Out-of-Battery - The status of a weapon before the action has returned to the normal, fully closed, firing position.
P Parallax - The difference between the bore axis or projectile trajectory versus the point of aim described by the aiming device (sights or optics).
Parkerizing (Phosphating) - A method of protecting a steel surface from corrosion and increasing its resistance to wear through the application of an electrochemical phosphate conversion coating.
Percussion Cap - A small cylinder enclosing a shock-sensitive material which creates energy, when struck by a hammer, which enables ignition of a propellant charge.
Picatinny Rail (MIL-STD-1913, Standardization Agreement 2324) - A bracket which provides a standard mounting platform for accessories and attachments.
Pistol – A firearm (handgun) that is designed to be fired held in one hand.
Point Blank – Any distance over which the trajectory of a given projectile fired from a given weapon remains sufficiently flat that one can strike a target by firing at it directly (that is, without hold-over or hold-under).
Porting – Openings at the muzzle end of the gun through which expanding gases can escape to help counteract perceived recoil and muzzle rise.
Printing – Typically, the visibility of a concealed handgun through the wearer's clothing.
Pump-Action - A type of firearm action in which the grip or charging handle can be pumped back and forth to eject a spent round and chamber a new, unfired cartridge.
Q
R Rate of Fire (RoF) - The frequency at which a firearm can fire its projectiles.
Receiver - The part of a firearm that houses the operating parts.
Recoil - The rearward momentum of a gun when it is discharged.
Red Dot Sight (RDS) - A type of reflex sight for firearms that gives the uses a red light-emitting diode (LED) as a reticle to create an aiming point.
Reticle – The aiming point seen in the center of a firearm scope that serves to indicate the expected point of impact of the fired projectile.
Revolver - A repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing.
Ricochet - A rebound, bounce or skip off a surface by a projectile.
Rifling - Helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis, which serves to stabilize the projectile in flight.
Rimfire - A type of firearm or cartridge which uses a firing pin or hammer to strike the cartridge base's rim to ignite it the propellant.
Rolling Block - A type of firearm action where the sealing of the breech is done with a circular shaped breechblock able to rotate on a pin.
Round - Synonymous with cartridge.
S Sabot - A device used in a firearm to fire a projectile that is smaller than the bore diameter.
Safety - Any mechanism used to help prevent the accidental discharge of a firearm. May be active (manual), such as thumb safeties, or passive (automatic), such as grip or trigger safeties.
Scope – A optic, usually magnified, used to aim a firearm.
Second Amendment (to the United States Constitution) – The second article in the United States Bill of Rights which guarantees the right to firearms. The Second Amendment reads "A well regulated militia being necessary for a free state, the right of the people to keep and bear arms shall not be infringed."
Select Fire - A firearm that fires semi–automatically and at least one burst or automatic mode by means of a selector depending on the weapon's design.
Short Barreled rifle (SBR) - A legal designation in the United States, referring to a shoulder-fired, rifled firearm with a barrel length of less than 16" or overall length (OAL) of less than 26".
Sight Picture – The shooter's view, comprised of the aiming device and the target, when aiming a firearm.
Sight Radius – The distance between the rear sight and the front sight.
Single-Action - A type of firearm action in which the manipulation of the trigger serves only to release the hammer or firing pin (but not cock it).
Single-Shot - A firearm that holds only a single round of ammunition, and must be manually reloaded after each shot.
Slamfire - A discharge, either intentional or unintentional, of a firearm that occurs as the bolt or breechface slams closed onto the cartridge.
Slide Bite - A phenomenon in which the web of the shooting hand is cut or abraded by the rearward motion of a pistol's slide.
Sling - A strap attached, generally to a rifle, used to stabilize the firearm for greater precision in shooting and/or to carry the firearm without occupying the shooter's hands.
Snubnose - Typically refers to a revolver with a short barrel.
Speedloader - A device used for loading a firearm or firearm magazine with loose ammunition quickly.
Squib - An ammunition malfunction in which a fired projectile does not have enough propellant force to exit the barrel, and thus becomes stuck. Subsequent firing without clearing the stuck projectile can result in catastrophic failure and injury to the shooter.
Stock - The part of a firearm to which the barrel and action are attached, that is typically held against the shooter's shoulder when firing for stability.
Stripper Clip - A speedloader that holds several cartridges together in a single unit for easier loading of a firearm's magazine.
Silencer (Suppressor) - A device intended to reduce the amount of noise generated by firing a weapon.
T Terminal Ballistics - A sub-field of ballistics, is the study of the behavior of a projectile when it strikes a target.
Trajectory – The arc described by a projectile as it travels from muzzle to point of impact.
Trigger - A mechanism that actuates the firing sequence of a firearm.
U
V
W Wadcutter - A special-purpose bullet specially designed for shooting paper targets with a flat or nearly flat front that cuts a very clean hole through the paper target, making it easier to identify the point of impact as it relates to scoring zones on the target.
Windage - The side-to-side adjustment of a sight, used to change the horizontal component of the aiming point.
X
Y
Z Zero - As a verb, the act of setting up a sighting system so that the point of impact of a bullet matches the point of aim at a specified distance.