A
ACP: An acronym for Automatic Colt Pistol, a type of ammunition used in semi-automatic pistols.
Action: The mechanism that handles the loading, firing, and ejection of cartridges in a firearm.
Ammunition: The material fired, scattered, dropped or detonated from any weapon, as bombs or rockets, and especially shot, shrapnel, bullets, or shells fired by guns.
AR: Stands for ArmaLite Rifle, not assault rifle as commonly misunderstood. It is a lightweight semi-automatic rifle.
AR-15: A lightweight, magazine-fed, gas-operated, air-cooled, shoulder-fired rifle. Originally designed by ArmaLite as a selective fire weapon for military use, the AR-15 was later adapted for civilian use in semi-automatic versions.
Assault Rifle: A rapid-fire, magazine-fed automatic rifle designed for infantry use.
Automatic: A firearm designed to feed cartridges, fire them, eject their empty cases and repeat this cycle as long as the trigger is depressed and cartridges remain in the feed system.
ATF: Acronym for the Bureau of Alcohol, Tobacco, Firearms and Explosives, a federal law enforcement organization within the United States Department of Justice. The ATF enforces laws and regulations related to firearms, explosives, arson, and alcohol and tobacco trafficking.
B
Ballistics: The science of projectiles and firearms, or in other words, the info about the bullet’s trajectory from when it leaves the barrel till the point of impact.
Barrel: The long, metal tube that guides the projectile out of the firearm.
Bolt Action: A type of firearm action where the handling of cartridges into and out of the weapon’s barrel chamber is operated by manually manipulating the bolt directly via a handle, which is most commonly placed on the right-hand side of the weapon.
Bore: The interior of a firearm’s barrel excluding the chamber. It can also refer to the caliber, or diameter of the interior of the barrel.
Brass: A slang term sometimes used for fired cartridge cases.
Break-Action: A firearm whose barrels are hinged and can be opened to expose the breech to allow direct loading and unloading of cartridges. Common in shotguns and some rifles and handguns.
Buffer: A device found in some automatic and semi-automatic firearms that reduces recoil and wear by absorbing energy from the moving parts after firing.
Bullet: The projectile expelled from the barrel of a firearm.
Buttstock: The rear part of a firearm that the shooter braces against the shoulder when firing. It helps stabilize the firearm and absorb recoil.
C
Caliber: The internal diameter or bore of a gun barrel.
Carbine: A carbine is a long gun with a shorter barrel than a rifle, making it lighter and more compact. Originally designed for cavalry use, carbines are now popular for various types of shooting due to their maneuverability.
Cartridge: A single unit of ammunition consisting of the case, primer, propellant, and projectile(s).
Chamber: The portion of a firearm’s barrel or action designed to hold a cartridge ready for firing. The chamber’s dimensions must match the cartridge for which the firearm is designed.
Choke: A constriction near the muzzle end of a shotgun’s barrel that shapes the spread of the shot to increase accuracy or range. Chokes can be fixed or interchangeable.
Clip: A device that holds multiple cartridges together for quick and easy loading into a magazine. Often confused with a magazine, clips are used to speed up the process of loading firearms with internal magazines.
Compensator: A muzzle device attached to the end of a firearm’s barrel designed to redirect propellant gases to reduce recoil and muzzle rise during shooting.
Cylinder: In revolvers, the cylinder is the rotating part that holds the ammunition in individual chambers. It aligns each chamber with the barrel sequentially as the gun is fired or prepared to fire.
Carbine Conversion Unit (CCU): A kit that allows a handgun to be converted into a carbine, typically by adding a longer barrel, shoulder stock, and sometimes an extended magazine. It offers greater stability and accuracy while maintaining the handgun’s firing mechanism.
Centerfire: A type of cartridge where the primer is located in the center of the base of the casing. Centerfire cartridges are known for their reliability and are reusable, as opposed to rimfire cartridges where the primer is in the rim.
D
DAO (Double Action Only): A type of firearm mechanism where pulling the trigger both cocks and releases the hammer or striker. This action means every shot requires the same amount of trigger pull, as opposed to firearms with a single-action/double-action (SA/DA) mechanism.
Decocker: A mechanism on some firearms that safely lowers the hammer without firing the gun, even if a round is chambered. This allows the firearm to be made safe without needing to pull the trigger.
Derringer: A small-sized handgun that is neither a revolver nor a semiautomatic pistol. Traditionally, derringers are single-shot or double-barrel firearms without a magazine, designed for concealed carry.
Drift: The lateral movement of a bullet’s path due to wind or other factors. In gunsmithing, it can also refer to the act of adjusting the sights of a firearm.
Drop Safety: A safety feature designed to prevent a firearm from discharging if dropped. This is achieved through various internal mechanisms that block the firing pin or hammer unless the trigger is deliberately pulled.
Dry Firing: The practice of pulling the trigger on an unloaded firearm. This is often done for training purposes, to practice trigger pull and handling without expending ammunition. However, not all firearms are designed to be dry-fired without potentially causing damage.
Dummy Rounds/Snap Caps: Inert rounds that contain no primer, propellant, or explosive charge, used for training, function testing, or dry firing. They simulate the weight and feel of live ammunition.
Dust Cover: A movable cover or plate on a firearm that prevents dust, dirt, and debris from entering the action, especially when the action is open or during operation.
E
Ejector: A mechanism in a firearm that removes spent cartridges or shells from the chamber after firing. In semi-automatic and automatic firearms, this is typically part of the cycling operation, whereas in revolvers, shotguns, and some rifles, it may require manual operation.
Elevation: The adjustment of a firearm’s sights or scope to ensure accuracy in vertical alignment, compensating for bullet drop over distance. Elevation adjustments help shooters aim correctly at targets at various ranges.
Energy (Muzzle Energy): The kinetic energy of a bullet as it leaves the muzzle of a firearm, typically measured in foot-pounds (ft-lbs) or joules. Muzzle energy is a function of both the bullet’s weight and its velocity upon exiting the barrel.
Engagement Distance: The range at which a firearm or weapon system is effectively used against a target. This can vary widely based on the type of firearm, ammunition, and intended use (e.g., close-quarters combat vs. long-range shooting).
Extractor: A part of a firearm that grips the rim or base of a cartridge or shell to pull it out of the chamber once it has been fired. The extractor works in conjunction with the ejector to remove spent casings from the firearm.
Eye Relief: The distance from the rear lens of a scope or optical sight to the shooter’s eye that allows for a full field of view and comfortable viewing. Proper eye relief is important for both comfort and safety, especially to avoid recoil-induced injuries.
Extended Magazine: A magazine that holds more rounds of ammunition than the standard capacity for a particular firearm. Extended magazines are available for many types of firearms and can increase the time between reloads.
External Safety: A manual safety mechanism located on the outside of a firearm’s frame or receiver. It typically requires manual operation to engage or disengage, preventing the firearm from firing when engaged.
Extractor Rod: In revolvers, an extractor rod is used to eject spent casings from the cylinder. Pressing the rod typically activates an extractor star, which pushes all casings out simultaneously for quick reloading.
Expanding Bullet: A bullet designed to expand upon impact, increasing its diameter to create a larger wound channel and transfer more energy to the target. Common types include hollow-point and soft-point bullets, often used in hunting and self-defense scenarios.
Eye Dominance: The tendency to prefer visual input from one eye over the other, which can influence aiming and shooting accuracy. Knowing one’s dominant eye is important in correctly aligning sights and achieving consistent aim.
F
Failure to Feed (FTF): A malfunction in a firearm where the ammunition fails to properly feed into the firing chamber from the magazine or belt. This can be caused by magazine issues, faulty ammunition, or problems with the firearm’s action.
Failure to Fire (FTF): A situation where pulling the trigger does not result in a discharge. This can be due to a faulty firing pin, defective ammunition (such as a bad primer), or other mechanical issues.
Failure to Eject (FTE): A malfunction where the spent casing is not fully ejected from the firearm’s chamber after firing, often resulting in a stovepipe jam or double feed.
Felt Recoil: The backward momentum felt by the shooter when a firearm is discharged. It is a subjective measure, influenced by the firearm’s design, the weight of the firearm, the power of the ammunition used, and the shooter’s technique.
Firearm: A portable gun designed to be carried and used by a single individual. It discharges bullets, shot, or shells by the explosive expansion of gases from the burning of gunpowder or another propellant.
Firing Pin: A small rod or pin in a firearm that strikes the primer of a cartridge, igniting the propellant and firing the bullet.
Fixed Sights: Non-adjustable aiming aids on a firearm, consisting of a front sight and a rear sight that are permanently attached and aligned. They require the shooter to adjust aim rather than the sights themselves for accuracy.
Flash Hider (or Flash Suppressor): A muzzle device that reduces the visible muzzle flash produced when a gun is fired. This helps preserve the shooter’s night vision and makes it harder for adversaries to spot the shooter based on the muzzle flash.
Flat Nose Bullet: A type of bullet with a flat front surface. It is often used in lever-action rifles with tubular magazines for safety reasons, as the flat nose prevents a bullet from setting off the primer of the cartridge in front of it under recoil.
Follower: The part of a magazine that pushes the cartridges or shells upwards, positioning them to be fed into the firearm’s chamber. It typically moves under the pressure of a spring.
Full Metal Jacket (FMJ): A type of bullet with a soft core (usually made of lead) encased in a shell of harder metal. FMJ bullets are designed to penetrate targets without expanding or fragmenting.
Furniture: The term used to describe the various wooden or synthetic parts of a firearm that serve as the stock, grip, or forend.
Fouling: The accumulation of residue inside the barrel and action of a firearm, left by bullets, powder, and primers after firing. Excessive fouling can affect accuracy and functioning.
G
Gas Block: A component on gas-operated firearms that regulates the amount of propellant gas diverted from the barrel to operate the weapon’s cycling mechanism. It is crucial for ensuring reliable operation and can sometimes be adjustable to accommodate different ammunition or suppressor use.
Gas-Operated Action: A type of firearm mechanism where a portion of the high-pressure gases from the fired cartridge is used to power the extraction and ejection of the spent case and the chambering of a new round. This system reduces recoil and increases the rate of fire.
Gauge: A measurement of shotgun bore diameter based on the number of lead balls of bore diameter needed to weigh one pound. For example, a 12-gauge shotgun has a bore diameter that would fit a lead ball weighing 1/12th of a pound. Smaller numbers indicate larger diameters.
Grip: The part of the firearm designed to be held by the hand. Grips can vary widely in shape, size, and material, including wood, plastic, or metal, and are often customizable for comfort or performance enhancements.
Grip Safety: A safety mechanism found on some firearms (notably, many models of 1911 pistols) that requires the grip to be fully compressed for the gun to fire. This helps prevent accidental discharges if the firearm is dropped or mishandled.
Grooves: The spiral cuts into the bore of a firearm barrel that impart spin to the bullet. This spin stabilizes the bullet in flight, increasing accuracy. The raised portions between the grooves are called “lands.”
Gunsmith: A professional who repairs, modifies, designs, or builds guns. Gunsmiths must have a thorough understanding of the mechanical function of guns, as well as skills in metalworking, woodworking, and sometimes even custom design or engraving.
Gunpowder: Also known as black powder, it was the first chemical explosive and the only one known until the mid-19th century. Modern firearms use smokeless powder, which is more powerful and produces less smoke and fouling.
Gun Locker: A secure storage solution for firearms, typically made of metal and lockable, to prevent unauthorized access. Sizes and security features vary, with some designed to be fireproof or to offer quick access in an emergency.
Gun Range: A specialized facility designed for firearms training, practice, and competition. Ranges can be indoor or outdoor and may have restrictions on the types of firearms and ammunition used.
H
Hammer: The part of a firearm that strikes the firing pin or the cartridge primer directly, causing ignition of the propellant. In many firearms, the hammer must be cocked either manually or by the action of the gun before it can fire.
Handguard: A component of a firearm located around the barrel or the front part of the gun to protect the shooter’s hand from the heat generated during firing and to provide stability and support.
Handgun: A firearm designed to be handheld, in either one or both hands. This class includes pistols (semi-automatic firearms) and revolvers (firearms with a revolving cylinder containing multiple chambers).
Handloading: The process of reloading firearm cartridges or shotgun shells by assembling individual components (case/hull, primer, powder, and bullet/shot), rather than purchasing completely assembled, factory-loaded ammunition. This allows shooters to customize loads for specific purposes.
Hang Fire: A delay between the triggering of a firearm and the ignition of the propellant. This condition can be dangerous, as it may lead to an unexpected discharge of the firearm.
Hardball: Slang for full metal jacket (FMJ) bullets, which are bullets encased in a shell of hard metal (typically copper) to reduce deformation upon firing and to penetrate targets more effectively. Commonly used in military ammunition.
High-Capacity Magazine: A term often used to describe a magazine that can hold more rounds than what is considered standard for a particular firearm. The exact definition can vary depending on laws and regulations in different jurisdictions.
Hollow-Point Bullet: A type of bullet designed to expand upon impact, maximizing tissue damage and stopping power. These are commonly used in law enforcement and self-defense situations but are restricted in international warfare under the Hague Convention.
Hoplophobia: An irrational fear of firearms or armed citizens.
Hydrostatic Shock: The theory that a bullet can produce a shockwave inside the body upon impact, causing damage to internal organs and tissues distant from the bullet’s path.
I
Ignition System: The mechanism in a firearm that initiates the firing process. Common types include flintlock, percussion cap, and centerfire primer systems.
Impact Point: The exact point where a projectile hits the target. It is used to adjust aiming or to calculate ballistics.
Intermediate Cartridge: A type of ammunition designed to have effectiveness and range between that of a full-power rifle cartridge and a shorter-range pistol cartridge. Examples include the 5.45×39mm NATO and 7.62×39mm cartridges.
Internal Ballistics: The study of the processes originally set in motion by the ignition of the propellant until the projectile exits the barrel, including the burning of the propellant, the movement of the projectile through the barrel, and the gas pressures developed.
Iron Sights: A system of aligned markers (sights) used to assist in the aiming of a weapon. They are called “iron” to distinguish them from optical and laser sights.
J
Jacket: The outer covering of a bullet, typically made from copper or a copper alloy. Jackets can cover the entire bullet or just a portion of it (as in semi-jacketed bullets). They help to prevent lead fouling in the barrel and can control expansion upon impact.
Jacketed Hollow Point (JHP): A type of bullet that has a hollowed-out center and a metal jacket covering the base and sides, but not the tip. This design allows the bullet to expand upon impact, increasing its stopping power while limiting over-penetration, making it popular for self-defense and law enforcement use.
Jammed Firearm: A condition where a firearm fails to function properly due to a malfunction in the cycling process, often caused by a failure to feed, extract, or eject a cartridge. Clearing jams requires specific procedures depending on the firearm and type of jam.
JSP (Jacketed Soft Point): A type of bullet designed to expand on impact but at a slower rate than a hollow point bullet. It features a soft lead core partially enclosed by a harder metal jacket, which exposes the soft point at the tip. This design offers a balance between penetration and expansion, making it suitable for hunting larger game.
K
Kick: Informal term for recoil or the backward movement experienced when firing a firearm. The “kick” is caused by the laws of physics (for every action, there is an equal and opposite reaction), where the forward motion of the bullet results in an equal force pushing back against the firearm and, consequently, the shooter.
Knockdown Power: An informal term used to describe the ability of a bullet or cartridge to physically knock down a target upon impact. While widely used among shooters and in media, the concept is scientifically inaccurate because the force imparted by a bullet is not sufficient to “knock down” a person or animal in the way often depicted. Instead, the term loosely relates to the stopping power or effectiveness of ammunition in causing incapacitation.
L
Lands and Grooves: In rifled barrels, lands and grooves are the raised and lowered sections, respectively, inside the barrel. The lands make contact with the bullet, imparting a spin around its longitudinal axis as it travels down the barrel. This spin stabilizes the bullet, improving accuracy over distance. The number and configuration of lands and grooves can vary between different firearms.
Laser Sight: A gun sight that uses a laser to project a dot or other marking onto a target, indicating where the bullet will strike if the firearm is properly aimed and fired. Laser sights can be mounted on various parts of a firearm and are useful for low-light conditions or rapid target acquisition.
Lever Action: A type of firearm action most commonly found on rifles and some shotguns. The shooter operates a lever (typically located around the trigger guard area) to eject a spent cartridge, cock the hammer (if necessary), and load a new cartridge into the chamber. Lever-action firearms are known for their reliability and faster rate of fire compared to bolt-action types, making them popular for hunting and historical reenactments.
Lock Time: The time interval between the trigger being pulled and the firing pin striking the primer to ignite the cartridge. Shorter lock times can contribute to better accuracy, as there is less opportunity for the shooter to move the firearm off target between these two events.
Long Gun: A general term used to describe firearms with longer barrels, such as rifles and shotguns. Long guns are typically held against the shoulder during firing and are used for hunting, sport shooting, and military applications due to their enhanced accuracy and range compared to handguns.
M
Magazine: A device that holds and feeds cartridges into a firearm’s chamber. Magazines can be detachable or integral to the firearm. They come in various forms, including box, tubular, and drum magazines, and are essential for repeating firearms to function smoothly and reliably.
Magnum: A term used to describe a cartridge that is more powerful than standard cartridges of the same caliber. Magnum cartridges typically have longer cases and more propellant, resulting in higher velocities and greater stopping power. They are often used for hunting larger game.
Manual Safety: A mechanism on a firearm designed to prevent the firearm from firing. Manual safeties can be found in various forms, such as thumb safeties, cross-bolt safeties, and grip safeties. Their primary purpose is to provide an additional layer of safety by physically blocking the firearm’s firing mechanism.
Match Grade: Refers to firearms, ammunition, or components that are designed or modified to have tighter tolerances and higher precision, making them suitable for competitive shooting. Match grade equipment is often more expensive due to the increased quality and performance standards.
Misfire: A failure of a firearm to discharge a round as expected after the trigger is pulled. Misfires can result from a variety of issues, including faulty ammunition, improper seating of the cartridge, or mechanical failures within the firearm. Proper handling and safety procedures should be followed in the event of a misfire.
MOA (Minute of Angle): A unit of angular measurement used to describe the accuracy and precision of firearms, particularly in target shooting and hunting. One MOA at 100 yards is roughly equivalent to a 1-inch circle. A firearm that shoots 1 MOA is considered capable of shooting a 1-inch group at 100 yards.
Muzzle: The front end of a firearm barrel from which the bullet exits when fired. The design of the muzzle, including features such as muzzle brakes or flash suppressors, can influence recoil and muzzle flash characteristics.
Muzzle Brake: A device attached to or integral with the muzzle of a firearm that redirects propellant gases to counter recoil and unwanted muzzle rise. Muzzle brakes are commonly used on rifles and some handguns to improve shooter comfort and accuracy.
Muzzle Energy: The kinetic energy of a bullet as it is expelled from the muzzle of a firearm. It is a function of both the mass of the bullet and its velocity upon leaving the barrel. Muzzle energy is often used as a measure of the potential stopping power of a given cartridge.
Muzzle Flash: The visible flame or blast emitted from the muzzle of a firearm when it is discharged. Muzzle flash is caused by the burning of propellant gases as they exit the muzzle. Various devices, like flash suppressors or flash hiders, are used to minimize muzzle flash for operational and safety reasons.
Muzzleloader: A type of firearm in which the projectile and usually the propellant charge are loaded from the muzzle (the open front end of the barrel) rather than from the breech (the rear end). Muzzleloaders were the dominant form of firearms until the mid-19th century and remain popular today for historical reenactments, hunting, and sport shooting.
Muzzle Velocity: The speed at which a projectile leaves the barrel of a firearm. Measured in feet per second (fps) or meters per second (m/s), muzzle velocity is a critical factor in determining a bullet’s trajectory, range, and kinetic energy. Higher muzzle velocities can result in flatter trajectories and more impact energy at the target. Factors influencing muzzle velocity include the type of propellant, the amount of propellant, the length of the barrel, and the mass of the projectile.
MRAD (Milliradian): An angular measurement used for adjusting firearm sights and scopes, equivalent to 1/1000th of a radian. One MRAD is approximately equal to 3.6 inches at 100 yards, or 10 centimeters at 100 meters. MRAD adjustments allow shooters to precisely dial in their aiming devices for accurate shots over varying distances. Scopes equipped with MRAD adjustments are favored by long-range shooters and snipers for their precision and ease of use across different measurement systems (metric and imperial). MRAD-based reticles facilitate quick adjustments without the need for complex calculations.
N
Negligent Discharge: An unintentional release of a firearm that occurs when the user fails to follow proper safety protocols, resulting in potential harm or damage.
NFA (National Firearms Act): Enacted in 1934, this pivotal U.S. legislation regulates the manufacture, transfer, and possession of certain types of firearms and accessories, including but not limited to short-barreled rifles, machine guns, suppressors, and destructive devices.
Nose: The forward-most section of a bullet or projectile. It plays a critical role in the aerodynamics and terminal performance of the bullet upon impact.
NRA (National Rifle Association): Established in 1871, the NRA is a U.S.-based organization that advocates for gun rights, while also providing firearm education, training, and safety programs.
Nickel-Plated: Firearms or ammunition components (typically casings) coated with a layer of nickel for enhanced corrosion resistance, smoother feeding in semi-automatic firearms, and aesthetic appeal.
O
Over-and-Under: A configuration of double-barreled shotguns where one barrel is mounted above the other. This design is favored for its balanced feel and is popular among sport shooters and hunters.
Overtravel: The movement of a trigger after the firing mechanism has been activated. Minimizing overtravel can improve shooting accuracy by reducing unnecessary movement that might disturb aim.
O-Ring: A circular gasket made of rubber or other flexible materials used in firearms to seal interfaces and prevent gas leaks, especially in suppressors and gas-operated firearms.
Overpressure Ammunition: Ammunition loaded to generate higher internal pressures than standard for the caliber, resulting in higher muzzle velocities and energy. Overpressure rounds are marked with a “+P” or “+P+” designation and should only be used in firearms rated for such loads.
P
Parallax: An optical phenomenon where the position or direction of an object appears to differ when viewed from different lines of sight. In firearms, parallax issues can affect accuracy when using scopes, as the reticle may not be properly aligned with the target at varying distances.
PCC (Pistol Caliber Carbine): A type of firearm that is similar in design to a rifle but is chambered to fire pistol-caliber ammunition. PPCs combine the accuracy and ease of handling characteristics of rifles with the reduced recoil, cost, and noise of pistol ammunition. They are popular for sports shooting, home defense, and plinking due to their versatility and the wide availability of pistol ammunition. Pistol Caliber Carbines often feature magazines compatible with popular handguns, making them an attractive option for shooters who already own pistols in the same caliber, allowing for magazine interchangeability and ammunition commonality.
Picatinny Rail: A bracket used on some firearms that provides a standard mounting platform for accessories such as optics, tactical lights, and laser aiming modules. The Picatinny rail has a series of ridges with a consistent spacing of .206 inches.
Pistol Grip: The handle of a firearm or where the shooter’s trigger hand grasps the gun. Pistol grips are found on handguns and are also a feature on some types of rifles and shotguns, providing ergonomic advantages.
Plated Bullets: Bullets that have been coated with a thin layer of metal, typically copper, through electroplating. Plating reduces lead exposure during handling and firing and can lead to cleaner barrels and reduced fouling.
Ported Barrel: A barrel with slots or holes drilled near the muzzle to direct some of the gases upward or to the sides, reducing recoil and muzzle rise.
Primer: A small ignition component that, when struck by the firing pin, ignites the propellant powder in a cartridge. Primers are a critical component in both rimfire and centerfire ammunition.
Propellant: The chemical mixture that, when ignited, generates gas to propel a bullet or projectile from a firearm. Historically referred to as gunpowder, modern firearms use smokeless powder as a propellant.
Pump Action: A type of firearm mechanism where the user manually cycles the action by moving a fore-end or slide back and forth. This action ejects the spent casing and chambers a new round. Commonly seen in shotguns and some types of rifles.
Q
Quadrail: A type of firearm handguard that includes four Picatinny rails positioned at the top, bottom, and sides. This configuration allows for the attachment of a wide range of accessories, such as lights, laser sights, grips, and bipods. Quadrails offer versatility for customization according to the shooter’s needs.
Quick Detach (QD) Mount: A type of mounting system used for attaching scopes, slings, and other accessories to firearms. Quick detach mounts allow for rapid installation or removal without the need for tools. This feature is particularly useful for shooters who need to quickly adapt their firearms to different situations or for ease of maintenance.
R
Rail Mount: A mounting system found on firearms that allows for the attachment of accessories such as sights, scopes, tactical lights, and laser aiming devices. Rail mounts are integral to the modular design of many modern firearms, providing a standardized interface for customization.
Receiver: The part of a firearm that houses the operating parts, including the trigger mechanism, firing pin, bolt or breechblock, and often the magazine or ammunition feed system. The receiver is typically considered the central component of a firearm and is usually serialized for identification.
Recoil: The backward movement experienced when firing a firearm, caused by the momentum of the bullet and expanding gases pushing forward against the firearm. Recoil management is an important aspect of shooting technique and firearm design.
Red Dot Sight: A type of non-magnifying reflector (or reflex) sight for firearms that gives the user an aimpoint in the form of an illuminated red dot. Red dot sights are popular for their simplicity and speed of target acquisition.
Reloading: The process of making ammunition by assembling the individual components: cases, primers, powder, and bullets. Reloading can be a cost-effective way for shooters to obtain ammunition tailored to their specific needs and preferences.
Repeater: A firearm that holds multiple cartridges and allows the shooter to fire a shot, eject the spent casing, and load a new round into the chamber with each manual operation of the action. Types of repeaters include bolt-action, lever-action, pump-action, and semi-automatic.
Reticle: The crosshairs or aiming point in an optical device such as a scope. Reticles come in various designs and are used to assist with aim and sometimes range estimation or bullet drop compensation.
Revolver: A type of firearm with a revolving cylinder containing multiple chambers for individual cartridges. Revolvers are typically handguns but can also be rifles or shotguns. The design allows the firearm to fire several shots without reloading by rotating the cylinder to align each chamber with the barrel.
Rifling: The spiral grooves cut or forged inside the barrel of a firearm, designed to impart a spin to the projectile for improved stability and accuracy over distance. The area between the grooves is known as the “lands,” which make contact with the projectile.
Rimfire: A type of cartridge ignition system where the firing pin strikes the rim of the cartridge case, igniting the primer. Rimfire cartridges are typically small caliber, such as .22 Long Rifle, and are used for plinking, small game hunting, and training.
Round: A term used to refer to a single cartridge or shot. “Round” can encompass the entire unit of ammunition for firearms, including the case, primer, propellant, and bullet or shot.
S
Safety: A mechanism on a firearm designed to prevent the firing mechanism from operating. Safety mechanisms vary widely across firearm types and models but are universally intended to prevent accidental discharges.
Sawed-off Shotgun (Sawn-off Shotgun): A shotgun that has had its barrel shortened, reducing its overall length. This modification is often associated with increased spread of shot and ease of concealment. Depending on jurisdiction, sawed-off shotguns may be illegal or heavily regulated.
SBR (Short-Barreled Rifle): A rifle with a barrel length shorter than a certain length defined by law (commonly under 16 inches in the United States) or an overall length below a certain threshold. SBRs are regulated in many jurisdictions and may require special licensing.
Semi-Automatic Action: A type of firearm action that automatically reloads the next round into the chamber but requires a separate trigger pull for each shot. It uses the energy of one shot to reload the chamber for the next.
Shooting Stance: The position and posture a shooter adopts when firing, which can affect accuracy and recoil management. Common stances include the isosceles, Weaver, and modified Weaver stances.
Shotgun: A long gun designed to fire a large number of small projectiles (shot) with a single pull of the trigger, typically used for hunting birds and other small game, sport shooting, and, in some cases, self-defense.
Silencer (Suppressor): A device attached to the barrel of a firearm intended to reduce the noise, muzzle flash, and overall signature of firing. The term “suppressor” is technically more accurate, as these devices do not completely silence the firearm.
Single Action (SA): A type of firearm trigger mechanism where the trigger performs a single action, typically releasing the hammer or striker to discharge the firearm. Single-action triggers are common in revolvers and some semi-automatic pistols.
Slide: The upper part of a semi-automatic pistol that houses the barrel, firing mechanism, and breechblock, and moves backward upon firing to eject the spent casing and chamber a new round.
Snub-nosed Revolver: A revolver with a short barrel, typically under 3 inches, known for its ease of concealment. Despite the reduced sight radius and increased difficulty in aiming, it remains popular for close-quarters self-defense.
Spitzer Bullet: A type of bullet with a pointed tip, designed to improve aerodynamics and increase the range and accuracy over traditional round-nosed bullets.
Stock: The portion of a firearm to which the barrel and action are attached. Stocks are usually made of wood, metal, or synthetic materials and serve as the interface between the shooter and the firearm, helping to absorb recoil.
Submachine Gun: A fully automatic or selective-fire firearm that fires pistol-caliber rounds. Designed for close-range combat, submachine guns are compact and have a high rate of fire.
T
Tactical Light: A flashlight designed for attachment to a firearm for low-light shooting conditions. Tactical lights can be mounted on handguns, rifles, and shotguns and are used for illumination and sometimes for disorienting targets.
Terminal Ballistics: The study of how and what a projectile does upon impacting the target. It is a crucial aspect of ammunition design and testing, focusing on the effects on the target, including penetration, expansion, and the transfer of kinetic energy.
Trigger: The lever or mechanism that, when pulled or pressed, releases the hammer, striker, or firing pin, causing the firearm to discharge. Triggers vary in design, pull weight, and characteristics across different types of firearms.
Trigger Guard: A loop of metal or other material surrounding the trigger of a firearm. Its primary purpose is to help prevent accidental discharge by protecting the trigger from being inadvertently pulled.
Trigger Pull: The amount of force required to discharge a firearm by pulling its trigger. Trigger pull weights can vary significantly, with lighter pulls often preferred for precision shooting and heavier pulls for safety in certain contexts.
Twist Rate: The rate of spin imparted to a bullet by the rifling of a barrel, usually expressed in terms of inches per turn (e.g., 1 in 10 inches). The twist rate is critical for stabilizing the bullet in flight to achieve accuracy over distance.
Two-Stage Trigger: A type of trigger that requires the shooter to pull through two distinct stages of resistance before the firearm discharges. The first stage usually involves a light pull to a noticeable stop, followed by a heavier pull to release the firing mechanism.
U
Unload: The process of removing all ammunition from a firearm, including any rounds in the chamber, magazine, or cylinder, to ensure it is safe to handle.
Upper Receiver: In firearms such as the AR-15, the upper receiver is the part of the gun that houses the barrel, bolt carrier group, and charging handle, among other components. It attaches to the lower receiver, where the trigger assembly, magazine well, and stock are located.
Urban Rifle: A term sometimes used to describe a compact, lightweight rifle optimized for close-quarters use within urban environments. These rifles often feature shorter barrels and collapsible stocks for maneuverability in tight spaces.
V
Velocity: The speed of a bullet or projectile as it is propelled out of the barrel of a firearm. Measured in feet per second (fps) or meters per second (m/s), velocity is a critical factor in determining a bullet’s trajectory and energy.
Vertical Grip: An accessory attached to the forend of a rifle or shotgun to provide the shooter with a more ergonomic grip and to help stabilize the firearm during shooting. Vertical grips can be particularly useful in tactical situations or in competitive shooting.
Varmint Rifle: A type of rifle designed specifically for hunting small pests and game animals, such as rodents and rabbits. Varmint rifles are typically characterized by high-velocity calibers and precision accuracy over long distances.
W
Wadcutter (WC): A type of bullet with a flat front that is often used in target shooting because it punches clean holes in paper targets, making scoring easier and more precise.
Walk-Fire: A technique used in military training where soldiers fire their weapons while walking towards a target. This is practiced to improve accuracy and confidence in moving combat situations.
Windage: The adjustment of a firearm’s sights to compensate for the horizontal movement of the bullet caused by crosswinds. Windage adjustments help shooters aim more accurately at their intended target.
Wildcat Cartridge: A cartridge that has been modified from its original design to meet specific needs or preferences not met by standard ammunition. Wildcat cartridges can offer higher velocity, increased accuracy, or the ability to fit in a preferred firearm platform.
