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What Is an AR-15 Rifle - What Is an AR-15 Rifle: Definition, Understanding the Components and Capabilities - Mid State Firearms , Mid State Firearms

What is an AR-15? Exploring its Definition, Components, and Uses as a Rifle

The AR-15 is a marvel of U.S. firearms engineering. It’s no doubt one of the most popular firearms you can buy, and its sheer versatility is unmatched.

Since it’s an iconic piece, there are many myths and inconsistencies that surround its name, and lots of folks have it all wrong about its characteristics and use.

This guide serves to clear up every doubt you have about the AR-15, and help you understand exactly what is an AR-15 rifle, what it’s used for, its main parts and components, general purposes, and caliber recommendations.

Brief History Of The AR-15

Before we get to the definition of AR 15 rifles, let’s first cover an important history lesson regarding the origins of the AR-15 rifle.

The AR-15 is the single most prominent semi-auto assault rifle that’s sold in the US today.

Primarily manufactured in the 50s by ArmaLite, the firearms engineers responsible for its conception are Eugene Stoner, Bob Fremont, and Jim Sullivan.

The team wanted to make a versatile rifle for military service that’s powerful, lightweight, customizable, and suitable for ‘anyone who has never even fired a gun’ to shoot it with ease.

Sadly, the firearm didn’t enjoy a lot of success in the first years when it arrived on the market. At that time and era, people stuck to their M1-Garands and trusty shotguns.

Colt Took Over the AR-15 Rifle

Four years later, ArmaLite sold the design and rights of the AR-10 and AR-15 to Colt.

Colt was tasked to produce a firearm that would replace the jam-prone M-16 rifle with a more reliable semi-automatic version for the Vietnam War.

Once again, this new version was also called the AR-15 rifle, and it quickly rose to popularity in the 70s.

Today, there are more than 500 manufacturers of AR-15 rifles with average sales that can attest to the ingenuity of Eugene Stoner and his team.

What Defines a Rifle as an AR-15?

Now that the AR-15 is marketed more towards civilians and law enforcement, the AR-15 quickly gained its cult status as a semi-automatic rifle that anyone can customize, modify, and use for many different purposes.

In contrast to most ‘heavy-duty’ assault rifles, the AR-15 is lightweight and customizable enough with lots of different caliber varieties for any firearm enthusiast to turn it into a viable platform for sporting, hunting, and home defense.

The AR-15 consists of upper and lower receivers

  • Barrel and muzzle device;
  • Bolt carrier group;
  • Buffer and buffer spring;
  • Charging handle;
  • Fire control group;
  • Furniture;
  • Gas block and gas tube;
  • Magazine;
  • Receiver extension;
  • Sights.

The AR-15 combines different advanced materials, manufacturing, and a tailor-made concept that’s resource-friendly for most manufacturers to produce a modern sporting rifle for their brand. This allows users to customize it with different parts and different calibers.

The Signature Characteristics of AR-15s

Here are the signature characteristics of an AR-15 rifle:

Semi-automatic function: The AR-15 can fire a single round once you pull the trigger, in contrast to full-auto firearms that allow a continuous fire mode when holding the trigger.

Lightweight: The AR-15 rifle is lightweight enough to be considered a very viable, easy-to-carry sporting rifle for various competitions.

Accurate: The accuracy of the AR 15 rifle depends on the barrel and caliber that’s straightforward to customize according to the user’s needs.

Easy to operate: It’s easier to operate than other rifles like bolt-action rifles which makes it suitable for rookie shooters.

Low recoil: Depending on the power of the cartridge, the AR-15 is commonly regarded as a low-recoil weapon.

The Benefits of Owning an AR-15 Rifle

Being one of the most versatile platforms on the market, the AR-15 is the main choice of gun owners because of the many benefits it offers:

The AR-15 platform is one of the most versatile out there. It is a top choice for gun owners of every experience level, with several key advantages that make it unique:

Adaptability: The AR-15 rifle is viable for any application, be it home defense, sporting, hunting, or just plain fun for plinking outdoors.

Customization: With unmatched modularity in mind, the AR-15 rifle is built to be fully customized according to the users’ needs. The parts are almost completely swappable and compatible with a massive variety of parts that are easily available on the market for a fair price.

Accuracy: Most AR-15 brands offer superb craftsmanship, as can be seen by the quality barrel of many AR-15 rifles. Expect solid accuracy and precision shooting at several hundred-yard ranges.

Reliability: The AR-15 is definitely one of the most reliable rifles you can find. Even if you don’t find the feeding mechanism reliable enough, you’re free to swap out different triggers, magazines, BCGs, and other parts until you make it ‘sing’.

Different Applications of the AR-15 Firearm

Most people ask, ‘What is an AR-15 used for?’, and this is a common question. While safety is the main priority of the AR-15’s design, you can use the rifle for:


Since it’s a modular powerhouse, most hunters use the AR-15 for hunting because it’s easy to turn it into a .308 Winchester, .300 Blackout, or 6.5 Grendel platform that’s customizable with excellent optics for long-range applications.

Home Defense

The AR-15’s 5.56/.223 caliber has minimal penetration power, and it also has modifiable buttstocks equipped with shorter barrels which can turn it into a home defense machine for those tight corners.

Sporting Events

The AR-15 rifle is one of the most viable options for sporting because of its unmatched modularity, lightweight design, and 3-Gun competition suitability thanks to its flexible characteristics.

Step-By-Step Process of How the Ar-15 Works

Once you pull the charging handle, the bolt carrier group compresses the buffer spring of the AR-15 rifle. Then, there are eight main phases of how the AR-15 cycles:

Feeding: The bolt carrier group’s forward movement takes a cartridge from the magazine as teh mechanism travels forward to set up a round.

Chambering: The cartridge taken from the magazine is chambered into the barrel.

Lock up: Once the bolt pushes the cartridge into the chamber, the BCG spins the bolt counter-clockwise, which enables a lock-up of the lugs of the barrel.

Shooting: The rifle fires when you pull the trigger in which the hammer of the control group is released, striking the pin. Once it strikes the pin, the cartridge’s primer is impacted, ignites the bullet, and propels the bullet through the barrel.

Unlocking: Unlocking happens when the inert gas travels through the barrel into the gas block and the gas tube, and this unlocks the bolt once it pushes the BCG backwards.

Extracting: As the bolt and BCG goes backwards, an extractor claw snatches the rim of the cartridge, and while the bolt goes to the rear, it pulls the casing from the chamber.

Ejecting: Once the BCG pulls out the shell, the bolt continues to move and ejects the shell through the ejection port.

Cocking: Finally, the BCG continues to move backwards and cocks the hammer until it completely compresses the buffer spring, resetting the cycle very quickly.

The AR-15 Rifle is Customizable, Versatile, and the Parts Are Available

The best characteristic of the AR-15 rifle is that it allows users to fully modify, combine, and upgrade the components however they please and with little to no help from gunsmiths or tools.

A semi-automatic rifle like the AR-15 can be personalized in multiple ways, and there are lots of parts that can be combined, no matter which brand or manufacturer is in question.

Here are some of the most popular components for the AR-15 that are widely available on the market:

  • Barrels
  • Bolt carrier groups (BCGs)
  • Carrying straps
  • Charging handles
  • Grips
  • Handguards
  • Lights and optics (scopes, lasers, and sights)
  • Muzzles
  • Receivers
  • Stippling
  • Stocks
  • Triggers
  • Upper and lower receiver parts


What Does AR 15 Stand For?

AR in ‘AR-15’ means ‘ArmaLite Rifle’, the company that made the rifle in the 50s.

Today’s AR-15 rifle commonly refers to the civilian model of the semi-automatic AR-15 variant that doesn’t have the fully-automatic firing mode of the military model.

Is ‘AR’ the Abbreviation for Assault Rifle?

Contrary to popular belief, ‘AR’ is not the abbreviation for ‘assault rifle’, and it absolutely does not mean ‘assault rifle’, nor ‘automatic rifle’ for that matter.

This common misconception is attributed to how most people intuitively believe in the abbreviation and follow this logic.

Why Is the AR-15 Commonly Known as the “Black Rifle”?

The AR-15 is regarded as the “Black Rifle” because it uses black furniture like upper and lower receivers that are made of anodized black with metal parts that are parkerized in dark finishes.

This is why most people call it a ‘Black Rifle’.

What Is an AR-15 Classified As?

To answer the ‘What type of gun is an AR 15?’, any AR-15-style rifle that’s lightweight and has a semi-automatic mode is regarded as an AR-15 rifle. Another characteristic that helps with classification is that it’s based on a similar concept to the Colt AR-15 design of the 70s.

As for pistol-style AR-15 guns, any firearm that’s fitted with a barrel that’s less than 16 inches, and doesn’t have shoulder support, is legally classified as a pistol rather than a short-barreled rifle.

Why Is the AR-15 Considered as the Most Popular Rifle in the United States?

The AR-15 is a very popular rifle in the US because it’s suitable for any firearm enthusiast who likes to customize their platform with tactical gear, competitive sportsmen who use it for recreational shooting, as well as hunters who are looking for long-range rifles.

It’s ergonomic, lightweight, accurate, and reliable enough to be used by many gun enthusiasts for many different purposes.

What makes it special is the wide variety of affordable cartridges like .22LR, .223/5.56, and even 9mm pistol calibers that can be used by turning it into a pistol variant with conversion kits. Here lies the true potential power of the AR-15; total modularity as an AR 15 definition.


There’s no doubt that the AR-15 rifle is a staple of modern firearms engineering. It’s modular, available in full kits or customizable component kits, and you can find many different calibers and upper receiver kits that anyone can customize with lower receivers.

Most importantly, the AR-15 rifle is very easy to modify and customize and doesn’t require any tools for it. That’s why it’s regarded as the ‘LEGO set of firearms’.

The wide variety of aftermarket parts makes it a popular firearm platform on the market, and you can find all kinds of parts for it with constant availability and support.

We hope this guide answers your ‘What is an AR 15 rifle’ question. Feel free to contact us at Mid State Firearms or check out our wide range of AR-15 parts if you want to fully customize your AR-15 rifle and turn it into a platform that suits your sporting needs.

author avatar
ALLEN GEARHART Engineer / Owner
Co-owner of Midstate Firearms since 2014. Manufacturer, Online distributor specializing in Ar15, parts, & accessories.
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