Complete AR-15 Terminology Guide – AR-15 Glossary

A

AR-15
A lightweight, modular semi-automatic rifle platform popular for sporting, self-defense, and tactical applications. Known for its customizability.

Adjustable Gas Block
A component that regulates the amount of gas redirected from the barrel to cycle the firearm, allowing shooters to fine-tune performance and recoil.

Armor-Piercing
Due to its enhanced capabilities, ammunition designed to penetrate challenging targets, such as body armor or vehicle plating, is restricted in many jurisdictions.

A2 Front Sight
Many traditional AR-15 rifles use a fixed, triangular front sight post, often integrated with a gas block.

Ambidextrous Controls
Firearm controls (e.g., safety selector and mag release) are designed to be accessible from either side, making them easier for both right—and left-handed shooters to operate.

Anodizing
An electrochemical process is commonly applied to aluminum firearm parts to increase corrosion resistance and surface hardness.

Accurized
Refers to modifications or enhancements to improve a firearm’s precision and accuracy, often seen in rifles used for competition or long-range shooting.

Aluminum Receiver
A firearm receiver made from aluminum alloy offers a balance between strength and lightweight design, which is common in AR-15 platforms.

Arm Brace
A stabilizing accessory that attaches to the rear of a pistol-style firearm to enhance control and accuracy, often used with AR pistols.

B

Barrel Nut
A component that secures the barrel to the upper receiver and often supports the attachment of the handguard.

Barrel Twist Rate
Indicates the rate at which a bullet spins in the barrel, measured in inches per turn (e.g., 1:7 twist); affects bullet stabilization and accuracy.

Buffer Tube
The receiver extension, also known as the buffer extension, houses the buffer and recoil spring in an AR-15 and serves as the stock’s mounting point.

Bolt Carrier Group (BCG)
The heart of the AR-15’s action, the BCG, includes the bolt, carrier, gas key, and firing pin. It is responsible for chambering, firing, and ejecting rounds.

Boresight
A method to align the firearm’s sights or optics with the barrel, often using a laser or optical device, to speed up zeroing.

Binary Trigger
A trigger mechanism that fires one round on the pull and another on the release, increasing the firing rate while remaining semi-automatic.

Billet vs Forged
This refers to the manufacturing process of parts: billet parts are machined from a solid block, while forged parts are shaped under high pressure—each with pros and cons in durability and cost.

Back-Up Iron Sights (BUIS)
Secondary sights are used in case of optic failure; they are typically flip-up and mounted on the firearm’s rail system.

Blued Finish
A protective, corrosion-resistant steel finish created through oxidation gives the firearm a dark blue or black appearance.

Bolt Lock
A feature that holds the bolt open after the last round is fired allows quicker reloading and inspection of the chamber.

C

Charging Handle
The manual device cycles the bolt in an AR-15, chamber a round, or clear a malfunction.

Chamber
The part of the barrel where a cartridge is seated and fired; different chambers accept different calibers and pressures.

Cold Hammer Forged
A barrel manufacturing method where steel is shaped around a mandrel by hammers, creating a highly durable and accurate barrel.

Compensator
A muzzle device designed to reduce muzzle rise by redirecting gas upward, improving control during rapid fire.

Collapsible Stock
An adjustable stock that allows the user to change the rifle’s length of pull for improved ergonomics and portability.

Chrome-Lined Barrel
A barrel with a chrome interior coating that enhances durability, corrosion resistance, and ease of cleaning.

Caliber
A firearm’s barrel’s internal diameter is measured in inches or millimeters to classify ammunition size (e.g., 5.56mm, .223 Rem).

Carbine
A shorter, lighter rifle variant, ideal for close to mid-range shooting, typically featuring a barrel length under 16 inches.

Canted Sight
A backup or offset sight is mounted at an angle to allow quick transitions from optics to iron sights without removing the primary sight.

Complete Upper
A fully assembled upper receiver group can be mounted on a compatible lower, including the barrel, BCG, handguard, and charging handle.

Crimp
A fold or indentation in the cartridge’s case mouth secures the bullet and aids in consistent ignition and performance.

D

Drop-In Trigger
A self-contained trigger unit can be easily installed into a lower receiver without individual components, offering improved trigger pull and consistency.

Direct Impingement
A gas system design where gas is redirected from the barrel directly into the bolt carrier group, cycling the action—common in AR-15 platforms.

Dimpled Barrel
A barrel with small machined indentations to provide alignment and secure mounting points for gas blocks and other components.

Dust Cover
A protective flap on the upper receiver that keeps dirt and debris out of the ejection port when the firearm is not firing.

Dwell Time
The time gas pressure remains in the barrel after a round is fired, crucial for reliable cycling in semi-automatic firearms.

Delta Ring
A circular retaining ring secures drop-in handguards on older AR-15s; today, it is commonly replaced with free-float systems.

Dry Fire
When done correctly, pulling the trigger on an unloaded firearm to practice trigger control, aiming, or mechanical function is safe.

E

Ejector
A component inside the bolt pushes the spent casing out of the ejection port after firing.

Ejection Port
The opening on the upper receiver is where spent casings are expelled after firing.

Extractor
A part of the bolt that grabs the rim of a spent casing and pulls it out of the chamber during the cycling process.

Eye Relief
The distance between the shooter’s eye and the scope lens where a full-sight picture is visible is critical for comfort and safety.

Ergonomics
How well a firearm’s design fits and functions with the shooter’s body—grips, controls, and overall feel all contribute to good ergonomics.

End Plate
A metal plate at the rear of an AR-15’s lower receiver secures the buffer tube and sometimes offers sling attachment points.

Enhanced Trigger Guard
An upgraded, often enlarged trigger guard that allows easier access when wearing gloves and improves comfort.

F

Free-Float Handguard
A handguard that does not touch the barrel improves accuracy by reducing pressure on the barrel and allowing for better accessory placement.

Flash Hider
A muzzle device that disperses burning gases to reduce visible muzzle flash, improving shooter visibility in low-light conditions.

Flat-Top Upper
An upper receiver with a Picatinny rail instead of a built-in carry handle allows various optics and accessory options.

Forward Assist
A push-button on the upper receiver manually ensures the bolt is fully closed, which is proper in adverse conditions or malfunctions.

Firing Pin
A critical part of the bolt carrier group that strikes the primer of a cartridge, igniting the gunpowder and firing the round.

Front Sight Post
The upright aiming component of iron sights is typically used with a rear aperture for accurate aiming.

Fixed Stock
A non-adjustable rifle stock that offers stable shooting support but lacks the length adjustability of collapsible models.

Full-Auto (for educational purposes/legal clarification)
Refers to firearms capable of continuous fire with one trigger pull. Heavily restricted for civilian ownership under federal law.

Feed Ramp
A smooth, angled surface guides rounds from the magazine into the chamber during cycling.

Flip-Up Sights
Backup iron sights that fold down when not in use and flip up for aiming are ideal as a secondary option to optics.

G

Gas Block
A component mounted over the barrel’s gas port redirects gas into the tube to cycle the action. It is available in standard or adjustable models.

Gas Key
Also known as the carrier key, it’s attached to the top of the bolt carrier and directs gas from the gas tube into the carrier to cycle the bolt.

Gas System Length
The distance between the gas port and the receiver (common types include pistol, carbine, mid-length, and rifle-length) affects recoil and reliability.

Grips
Handles that the shooter holds, including pistol grips and vertical or angled foregrips, improving control and comfort.

Green Tip Ammo
M855 5.56 NATO ammunition with a steel core and green-painted tip. Known for better penetration; not classified as armor-piercing by federal law.

Gunsmith
A professional trained in firearm repair, customization, and maintenance. Essential for complex builds or modifications.

Gun Trust
A legal entity used to register and manage firearms (especially NFA-regulated items), allowing multiple trustees and smoother inheritance transfers.

Grip Angle
The angle at which the grip meets the firearm. Different angles affect wrist positioning, comfort, and control.

H

Handguard
A protective covering around the barrel that allows the shooter to hold the firearm safely. It also serves as a mounting platform for accessories like lights, grips, and lasers.

Headspace
Headspace is the distance between a cartridge’s base and the chamber’s part that stops forward movement. Proper headspace is critical for safe and reliable firearm operation.

Hammer
A component in the lower receiver that strikes the firing pin when released by the trigger, igniting the cartridge.

Heat Shield
A protective barrier built into or added to a handguard to reduce heat transfer from the barrel during extended firing sessions.

Heavy Barrel (HBAR)
A barrel with a thicker profile is commonly used in target or duty rifles. It offers increased accuracy and reduced barrel whip during sustained fire.

Hybrid Sight
A sight system that combines two aiming methods, such as red dot and magnifier or irons with optics, to enhance versatility in varied shooting scenarios.

Holographic Sight
A non-magnifying optical sight that uses laser-generated holograms to project a reticle, offering fast target acquisition and performance in low light or at odd angles.

H Buffer
A heavier buffer designed to slow the bolt carrier’s rearward movement, reducing felt recoil and improving reliability, particularly in over-gassed AR-15s.

I

Iron Sights
Mechanical aiming devices consist of a front and rear sight. Reliable and durable, they’re often used as backups to optics.

Inconel
A high-strength, heat-resistant metal alloy used in suppressors and gas system components for extreme durability under high temperatures.

Intermediate Gas
A less common gas system length that falls between mid-length and rifle-length, designed for smoother recoil and reliable cycling in 18” barrels.

Inside Diameter
A part’s internal measurement (e.g., handguard or barrel nut) must match compatible components for proper fit and function.

Impact Shift
A change in point of impact caused by altering optics, suppressors, or environmental conditions. It’s crucial to re-zero optics after any change.

Index Markings
Visual reference marks on barrels, gas blocks, and other components are used for precise alignment during assembly or maintenance.

J

JHP (Jacketed Hollow Point)
A type of bullet with a hollow tip and metal jacket designed to expand on impact. Common for self-defense due to its stopping power and reduced risk of over-penetration.

Jamming
A malfunction in which a firearm fails to cycle or eject properly. Causes vary from ammunition issues to improper lubrication or parts wear.

Jig (for 80% lowers)
A precision guide is used during the milling of 80% lower receivers to complete fire-control cavity cuts legally and accurately.

JP Enterprises (brand reference)
A high-end firearms manufacturer known for precision AR components like triggers, BCGs, and complete rifles optimized for competition and reliability.

K

KeyMod
An older modular accessory mounting system with keyhole-shaped slots. It allows the direct attachment of accessories without bulky rail sections.

Keyhole Forge Mark
A small keyhole-shaped symbol found on some forged AR-15 receivers identifies the forging origin—typically from Cerro Forge.

KAC (Knight’s Armament Company)
A premier defense contractor known for military-grade firearms, accessories, and suppressors, including the SR-25 and high-end handguards.

Krinkov-Style Muzzle Device
A conical muzzle device originally used on AKS-74U rifles. It redirects blast forward and reduces flash—popular on short-barreled rifles.

Kick (recoil slang)
A casual term for recoil—the backward force felt when firing a gun. Affected by caliber, firearm weight, and muzzle devices.

L

Lower Receiver
The serialized part of an AR-15 houses the trigger group and accepts magazines. Legally considered the firearm by the ATF.

LPK (Lower Parts Kit)
A collection of components required to complete the internal functions of a stripped lower receiver, including the trigger, pins, springs, and safety selector.

Lightweight Barrel
A thinner barrel profile is designed to reduce overall firearm weight. It is ideal for fast handling but may heat up faster under sustained fire.

Locking Lugs
Protrusions on the bolt head that lock into the barrel extension during firing ensure a secure and pressure-safe chamber seal.

Lapping Tool
A tool used to polish and square the mating surface of the upper receiver and barrel extension for improved accuracy and alignment.

Long Stroke Gas System
A type of operating system, like the AK-47, where the piston is attached to the bolt carrier, provides reliability under adverse conditions.

Linear Compensator
A muzzle device that directs blast and noise forward, away from the shooter and bystanders—popular for indoor or close-quarter shooting.

Loadout
A personalized selection of weapons, gear, and ammunition tailored for specific missions or roles, such as home defense, duty, or competition.

M

M-LOK
Magpul developed a modular mounting system that allows users to attach accessories directly to handguards using standardized slots, resulting in a sleek, lightweight setup.

Mil-Spec
Short for “military specification,” this term refers to parts and standards that meet the U.S. military’s requirements. It’s often used as a baseline for AR-15 component quality and compatibility.

Match Grade Barrel
A high-precision barrel manufactured to tighter tolerances, designed for competitive shooting and maximum accuracy.

Magazine
A detachable or fixed device that holds ammunition and feeds it into the chamber. AR-15s typically use 10-, 20-, or 30-round detachable box magazines.

Muzzle Device
An attachment at the end of the barrel, such as a flash hider, compensator, or muzzle brake, alters how gas exits the muzzle to affect recoil, flash, or blast direction.

M4 Feed Ramps
Angled cuts in the barrel extension and upper receiver help guide rounds from the magazine into the chamber, improving feeding reliability—especially in carbines.

Mid-Length Gas
A gas system configuration in AR-15s that balances carbine and rifle-length systems provides smoother cycling and reduced recoil in 16” barrels.

MOA (Minute of Angle)
A unit of angular measurement used in optics and accuracy discussions. 1 MOA equals approximately 1 inch at 100 yards.

Magwell
A magazine is inserted into the flared opening in the lower receiver. Some magazines are enhanced for faster reloads and better magazine alignment.

Monolithic Upper
A one-piece upper receiver and handguard design that improves rigidity and often contributes to better accuracy by eliminating flex points.

Manual Safety
A mechanical switch that prevents the firearm from firing when engaged, allowing the user to safely carry the weapon until ready to shoot.

Multi-Cal
Indicates that a lower receiver can accommodate multiple calibers, depending on the upper receiver and bolt carrier group used.

N

Nitride Finish
Also known as QPQ or Melonite, it is a heat-treating process that enhances surface hardness, corrosion resistance, and wear resistance on barrels and bolts.

NATO Rounds
Ammunition standardized by NATO countries. Examples include 5.56x45mm NATO and 7.62x51mm NATO, often similar to but not identical to their civilian equivalents.

NFA (National Firearms Act)
A federal law that regulates specific firearm types—like suppressors, short-barreled rifles (SBRs), and full-auto firearms—requires extra paperwork, taxes, and background checks.

Nickel Boron
Internal parts like BCGs and triggers are coated with a durable, corrosion-resistant material for smoother operation and easier cleaning.

Night Sights
Sights equipped with tritium or fiber optics for low-light shooting are commonly found on pistols and defensive rifles.

Non-Reciprocating Charging Handle
A charging handle that remains stationary while the firearm cycles is safer and more comfortable to operate. It is often seen on side-charging uppers or alternative platforms.

No-Go Gauge
Armorers use a headspace tool to verify that a chamber is not too long. If a bolt closes on a no-go gauge, it indicates an unsafe headspace.

O

Optics
Sight systems that enhance aiming accuracy, including red dots, scopes, and holographic sights. Essential for precision and target acquisition in modern shooting.

Overgassing
This occurs when too much gas enters the system, leading to excessive recoil and wear. It can be mitigated with an adjustable gas block or heavier buffer.

Offset Sights
Iron sights or optics mounted at a 45-degree angle serve as backups or close-range options alongside a primary magnified optic.

One-Piece Handguard
A free-float handguard that is machined as a single piece for increased strength, stability, and precision alignment with the upper receiver.

O-Ring Extractor
A rubber ring is added to the extractor spring in the BCG to enhance tension and reliability in extracting spent casings.

Overtravel (trigger)
The distance a trigger moves after releasing the sear. Excess overtravel can impact follow-up shots and trigger a reset feel.

P

Pistol Grip
The grip area behind the trigger is designed for improved weapon control. AR-15 pistol grips come in a wide variety of textures and angles.

Pistol-Length Gas System
The shortest common AR-15 gas system is used in barrels under 10.5 inches. It offers reliable cycling in compact platforms but can result in increased recoil and wear.

Picatinny Rail
A standardized mounting system consisting of a series of ridges and slots used to attach sights, scopes, and accessories.

Phosphate Coating
A corrosion-resistant surface treatment is commonly used on bolt carrier groups and barrels to enhance durability and lifespan.

Pin and Weld
A method of permanently attaching a muzzle device to extend barrel length legally, especially to meet the 16” rifle minimum without NFA classification.

Press Check
A manual method of partially retracting the bolt or slide to confirm whether a round is chambered without fully cycling the firearm.

Precision Rifle
A firearm optimized for extreme accuracy, often with match-grade barrels, enhanced triggers, and long-range optics.

Parts Kit
A bundled set of components to complete a firearm build commonly includes everything except the serialized lower receiver.

Parkerizing
A protective phosphate coating applied to steel firearm parts to resist rust and wear is often found on military-style firearms.

PDW (Personal Defense Weapon)
A compact firearm designed for close-quarters use, typically shorter than carbines and equipped with pistol braces or short barrels.

P-Mag
A popular polymer magazine brand made by Magpul and known for durability, reliability, and broad compatibility with AR-15 platforms.

Q

QD Sling Mount (Quick Detach)
A system allowing quick attachment and removal of slings via push-button swivels—commonly used for tactical flexibility.

Quick Change Barrel
A firearm feature that allows users to replace the barrel without tools or with minimal effort—ideal for multi-role rifles or rapid caliber changes.

Quenching (heat treatment process)
A rapid cooling process is used in metal treatment to harden firearm components, improving durability and lifespan.

QR Code Marking (on lowers or optics)
Digital identification marks are laser-etched on firearms or accessories for tracking, registration, or warranty purposes.

QPQ (Quench Polish Quench) Nitride
A form of nitride finish involving quenching, polishing, and re-quenching steel parts for enhanced hardness, corrosion resistance, and smooth surface finish.

R

Rail System
A mounting interface, such as Picatinny, M-LOK, or KeyMod, allows accessories like optics, lights, and grips to be attached to the handguard or upper receiver.

Red Dot Sight
A non-magnified optic that projects a red dot onto a lens for fast target acquisition and enhanced shooting accuracy, ideal for close to mid-range engagements.

Receiver Extension
Another term for the buffer tube on an AR-15, housing the buffer and recoil spring. It also serves as the mounting point for the stock.

Recoil Spring
Located inside the buffer tube, it helps absorb recoil and returns the bolt carrier group forward after firing.

Rifle-Length Gas
A gas system configuration typically used on 20” barrels, providing smoother operation and less wear due to lower gas pressure.

Rifling
The spiral grooves inside a barrel that spin-stabilize the bullet, increasing accuracy over distance.

Roll Pin
A cylindrical metal pin secures components like the trigger guard or forward assist within the receiver.

Rear Sight
Part of the iron sight system is located on or near the rear of the receiver and is used for aiming in alignment with the front sight.

Recce Rifle
Short for “reconnaissance rifle,” it’s a lightweight, accurate AR-style rifle typically with a free-float barrel and variable optic—bridging CQB and long-range roles.

Riser Mount
An accessory used to elevate optics or sights to achieve the desired height, often for better sight alignment or co-witnessing.

S

Semi-Automatic
A firearm action where one round is fired with each trigger pull, and the weapon automatically chambers the next round.

Safety Selector
A switch that enables or disables the firearm’s ability to fire. Standard options include “safe” and “fire,” with some models featuring ambidextrous selectors.

Suppressor
Also known as a silencer, this muzzle device reduces the sound of gunfire and muzzle flash. Requires an NFA tax stamp and approval for civilian ownership.

SBR (Short Barrel Rifle)
A rifle with a barrel shorter than 16 inches, regulated under the NFA. It requires special registration and a tax stamp for legal ownership.

Staking
A process used to mechanically secure fasteners, like the gas key screws on a BCG, preventing them from loosening under recoil and vibration.

Stripped Upper
An upper receiver without internal parts like the forward assist, ejection port cover, or BCG is ideal for custom AR builds.

Stock
The rear part of a rifle or carbine rests against the shooter’s shoulder, helping to stabilize the firearm during aiming and firing.

Side Charging Upper
An AR upper receiver design with a charging handle on the side instead of the rear allows faster, easier manipulation and clearing of malfunctions.

Sling
A strap attached to a firearm for carrying and stabilizing while shooting. Available in one-point, two-point, or three-point configurations.

Shot Placement
This refers to the accuracy and location of a bullet’s impact on a target. Proper shot placement is essential for effectiveness, especially in defensive or hunting scenarios.

Shell Deflector
A raised section near the ejection port on AR-15s that redirects spent casings away from the shooter’s face, particularly helpful for left-handed users.

T

Trigger Pull
The amount of pressure required to activate the trigger and fire the weapon is measured in pounds and affects shooting precision.

TDP (Technical Data Package)
A set of detailed specs and drawings defining “true mil-spec” AR-15 components was initially created for military contracts.

Thread Pitch
The number of threads per inch on a barrel’s muzzle, used to match muzzle devices like flash hiders or suppressors correctly.

Two-Stage Trigger
A trigger system has two separate stages: a light initial take-up and a crisp break. Popular in precision shooting for control and accuracy.

Tactical Light
A weapon-mounted flashlight designed for identifying targets in low-light environments. Some models include strobe or pressure switch functions.

Thermal Fit
A tight barrel-to-receiver fit achieved by heating the upper and chilling the barrel before installation—enhancing accuracy and rigidity.

Twist Rate
Refers to how fast the rifling spins a bullet, expressed as one turn in X inches (e.g., 1:7). It must match the bullet weight for optimal stability.

Takedown Pin
A pin separates the upper and lower receivers for maintenance or storage, while front and rear pins hold the AR-15 together.

Tapered Barrel
A barrel design that narrows from chamber to muzzle offers reduced weight while maintaining strength where needed.

Trunnion
A structural component often seen in AK-style firearms supports the barrel and bolt locking surfaces.

U

Upper Receiver
The top portion of an AR-15 that houses the BCG, barrel, and charging handle. It mates with the lower receiver to form the complete rifle.

UTG (brand)
A manufacturer known for affordable firearm accessories, including handguards, optics, bipods, and more.

Under-Gassed
A condition where insufficient gas reaches the BCG to cycle the action correctly, leading to weak ejection or failure to feed.

Upper Parts Kit (UPK)
A set of components used to complete a stripped upper receiver, typically including the dust cover, forward assist, and related pins and springs.

UBR Stock
A heavy-duty, fixed/adjustable hybrid stock from Magpul designed for balanced weight distribution and rugged use.

Uniform Bore Diameter
Refers to consistency in the internal diameter of the barrel, ensuring consistent pressure, velocity, and bullet trajectory.

V

Vortex Flash Hider
A spiral-pronged muzzle device known for excellent flash suppression and often used on military and tactical AR-15s.

Vertical Foregrip
A grip attached to the handguard’s underside offers enhanced control, especially during rapid fire or tactical movement.

Velocity
The speed at which a bullet travels upon leaving the barrel is typically measured in feet per second (FPS). This speed affects trajectory and energy on impact.

Vise Block
When placed in a vise, a tool is inserted into the magwell or upper receiver to stabilize the firearm during assembly or maintenance.

Varmint Barrel
A long, heavy barrel designed for small-game hunting and precision shooting. Offers high accuracy and heat resistance.

VLTOR (brand)
A manufacturer specializing in high-quality AR accessories, including enhanced buffer systems, stocks, and modular upper receivers.

Variable Optic
A rifle scope with adjustable magnification, such as 1-6x or 3-9x, offers flexibility between close-range and long-distance shooting.

W

Weaver Rail
An older mounting system similar to Picatinny but with smaller, less standardized slot spacing. Some modern accessories still support Weaver compatibility.

Windage
Horizontal adjustment of a sight or optic to align the point of aim with the point of impact. Critical for accurate shooting, especially at distance.

Weapon Light
A flashlight mounted to a firearm is used for target identification in low-light environments. It is often activated via a push-button or pressure switch.

Wylde Chamber (.223 Wylde)
A hybrid rifle chamber that safely and accurately fires both .223 Remington and 5.56 NATO ammo. Known for enhanced precision and versatility.

Weight Class (lightweight, heavy, etc.)
The build weight of a firearm or its components refers to the weight of the firearm itself. Lightweight builds prioritize maneuverability, while heavy builds often improve stability and heat resistance.

Weld Spring
A type of spring used in various firearm applications, such as holding pins or retaining parts. In ARs, often found in detents or buffer assemblies.

Witness Marks
Minor, intentional marks made during assembly to help verify alignment or torque—commonly used on gas blocks, barrel nuts, or scope mounts.

WML (Weapon-Mounted Light)
A tactical flashlight attached directly to a firearm for low-light operations. Enhances threat identification and target acquisition.

X

X-Ray Sights (e.g., SIG’s sights)
Factory night sights from SIG Sauer featuring high-visibility front sights and tritium illumination for enhanced aiming in daylight and low-light conditions.

Xtreme Duty Parts
A general term used for firearm components designed to withstand extreme use, stress, or harsh environments. Typically heavy-duty and overbuilt for reliability.

X-Series (brand/model designations)
Often used by manufacturers to identify enhanced or modular product lines—like SIG’s P320 X-Series or upgraded AR parts featuring advanced ergonomics.

Y

YHM (Yankee Hill Machine)
A respected manufacturer known for rugged suppressors, rails, and AR parts made in the USA. Offers value-driven components for builders and shooters.

Yoke
A rarely used term in AR platforms, sometimes referring to pivot components in bolt assemblies or buffer retainer systems. More commonly used in revolver construction.

Yaw (ballistics term)
Refers to the oscillation or deviation of a bullet’s nose from its flight path. Excessive yaw can reduce accuracy and cause instability.

Yugo Variant (AK crossover relevance)
A Yugoslavian variation of the AK platform with unique features like different trunnion sizes, furniture compatibility, and gas system specs—relevant for AK enthusiasts.

Z

Zeroing
The process of aligning your sights or optics so the point of aim matches the point of impact at a specific distance.

Zero Distance
The distance at which a firearm is zeroed. Standard zero distances for AR-15s include 36, 50, or 100 yards, depending on intended use.

Zinc Coating
A corrosion-resistant finish protects firearm components against moisture and rust. It is less common than phosphate or nitride coatings.

ZEV Technologies (brand)
A premium firearms manufacturer known for performance upgrades, especially for Glock pistols and AR components like upper receivers and triggers.

ZEV Upper
An upper receiver manufactured by ZEV Technologies typically offers precision machining, tight tolerances, and modular compatibility for custom AR builds.

ZQI Ammo (brand reference)
A brand offering affordable, military-grade ammunition for training and range use. Known for bulk 5.56 and 7.62 NATO offerings.