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AR-15 Glossary

Definitions for common AR-15 parts, specs, and terminology. From buffer weights to twist rates, everything you need to speak the language.

A

Adjustable Gas BlockAn adjustable gas block is a critical component in your AR-15’s gas system that allows you to fine-tune how much gas...Ambidextrous ControlsWhat Are Ambidextrous Controls on an AR-15? Ambidextrous controls, commonly called “ambi” controls in the AR-15...Armor PiercingArmor piercing ammunition for the AR-15 refers to specialized cartridges designed to penetrate hard targets, typically...

B

Ball AmmoBall ammo, also known as FMJ ammunition (Full Metal Jacket), is the standard military-style cartridge featuring a lead...Ballistic CoefficientThe ballistic coefficient (BC) is a numerical value that measures how well a bullet overcomes air resistance during...Barrel HarmonicsWhat Are Barrel Harmonics? Barrel harmonics refers to the vibration patterns that occur when a rifle barrel vibrates...Barrel WhipUnderstanding Barrel Whip in AR-15 Builds Barrel whip refers to the oscillating movement your rifle barrel experiences...Battery Assist DeviceBattery Assist Device: Essential AR-15 Component Explained A battery assist device , more commonly known as the forward...Blow ForwardWhat Is Blow Forward Action? A blow forward action firearm operates on an unconventional principle where the barrel...Bolt BounceWhat Is Bolt Bounce? Bolt bounce is an AR-15 malfunction where the bolt carrier group (BCG) rebounds off the buffer and...Bolt OverrideWhat Is a Bolt Override? A bolt override occurs when the bolt carrier group (BCG) travels over the top of a cartridge...Buffer WeightThe buffer weight is a critical component of your AR-15’s buffer system that directly impacts cycling reliability,...Bump FireWhat is Bump Fire? Bump fire is a shooting technique that uses the recoil energy of a semi-automatic rifle to rapidly...

C

Cam Pin RotationCam pin rotation refers to the rotational movement of the cam pin inside the bolt carrier group (BCG) during the...Carbon FoulingCarbon Fouling Carbon fouling is the accumulation of carbon deposits inside your AR-15 , primarily in the barrel,...Carrier TiltWhat is Carrier Tilt? Carrier tilt refers to the downward angle that occurs when an AR-15 bolt carrier group (BCG)...Case Head SeparationCase head separation occurs when the rear portion of a brass cartridge case detaches from the body during firing,...Chamber CastA chamber cast is a precise replica of your AR-15’s chamber created using Cerrosafe , a low-melting-point alloy that...Chrome Lining ProcessThe chrome lining barrel process involves electroplating a thin layer of hard chrome (typically 0.0002 to 0.0005...Cold Hammer ForgingCold Hammer Forging (CHF) is a barrel manufacturing process where a barrel blank is hammered around a precision mandrel...Controlled PairA controlled pair is a shooting technique where the shooter fires two rounds in rapid succession while maintaining...Crush WasherA crush washer is a deformable metal washer that sits between your muzzle device and barrel shoulder, providing proper...Cycle RateThe cycle rate of an AR-15 refers to how fast the bolt carrier group (BCG) completes its operational cycle: unlocking,...

D

Dead Air MountWhat Is a Dead Air Mount? A Dead Air mount refers to the proprietary suppressor mounting system developed by Dead Air...Double FeedA double feed is a Type 3 malfunction where two rounds attempt to enter the chamber simultaneously, creating a severe...

E

Extractor TensionWhat is Extractor Tension? Extractor tension refers to the spring force that keeps your AR-15 bolt’s extractor claw...

F

Failure to EjectFailure to eject (FTE) occurs when a spent casing fails to clear the ejection port after firing, often resulting in a...Failure to ExtractA failure to extract malfunction AR-15 occurs when the extractor fails to remove the spent casing from the chamber...Failure to FeedA failure to feed (FTF) is a malfunction where a cartridge fails to properly feed into the chamber from the magazine...Feed Ramp PolishingFeed ramp polishing is the process of smoothing and refining the angled surfaces that guide cartridges from the...Flash SignatureThe flash signature of your AR-15 refers to the visible flame and light produced when hot propellant gases exit the...

G

Gas Port SizeWhat is Gas Port Size? Gas port size refers to the diameter of the hole drilled through an AR-15 barrel that allows gas...Gas Ring TestThe gas ring test is a simple diagnostic procedure used to verify the proper function of gas rings on an AR-15 bolt....

H

Hammer FollowHammer follow is a dangerous trigger malfunction where the hammer rides the bolt carrier group forward after firing,...Headspace GaugeA headspace gauge is a precision measuring tool used to verify the critical distance between the bolt face and the...

I

In-BatteryWhen your AR-15 bolt is “in battery,” it means the bolt carrier group (BCG) has fully chambered a round and rotated...

K

Key HolingWhat is Keyholing? Keyholing occurs when a bullet tumbles in flight and strikes the target sideways rather than...

L

LockupLockup refers to the engagement between the bolt lugs and barrel extension lugs when an AR-15 bolt carrier group cycles...Lug EngagementLug engagement refers to the contact area between the bolt lugs and the corresponding lug recesses in the barrel...

M

Magazine Well FlareMagazine Well Flare A magazine well flare (often called a flared magwell or magwell funnel) is an aftermarket accessory...Mortar TechniqueThe mortar technique is an emergency malfunction clearing method used when standard tap , rack, bang procedures fail to...Muzzle BlastMuzzle blast refers to the explosive release of high-pressure gas that exits the barrel immediately after a bullet...Muzzle VelocityWhat Is Muzzle Velocity? Muzzle velocity measures how fast a bullet travels when it exits your rifle’s barrel,...

O

Over-GassedAn over-gassed AR-15 occurs when excess gas pressure flows back through the gas tube into the bolt carrier group ,...

P

Pinned and WeldedA pinned and welded muzzle device is a permanently attached muzzle device on an AR-15 barrel, created by drilling a...Projectile Grain WeightProjectile grain weight refers to the mass of a bullet measured in grains, where one grain equals 1/7000th of a pound...

R

Receiver ExtensionA receiver extension , commonly called a buffer tube , is the cylindrical aluminum component that threads into the rear...

S

Short StrokingShort stroking occurs when an AR-15’s bolt carrier group (BCG) fails to travel its complete rearward distance during...StakingStaking Staking is a mechanical deformation process used to permanently secure critical AR-15 components, specifically...Suppressor BackpressureSuppressor backpressure refers to the increased gas pressure that flows back through your AR-15’s gas system when using...