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The AR-15 is certainly the most popular rifle platform ever developed. Although it is impossible to know just how many of these lightweight, semi-automatic rifles there are in the United States, estimates fall somewhere between 5 million and 10 million.

The AR-15 rifle is often misunderstood. Few people (at least outside of shooting culture) truly understand its limitations and capabilities. In an attempt to educate the masses, we’re going to take a brief look at this iconic rifle’s storied past.

The ArmaLite Family Tree

Although Colt’s Manufacturing gets most of the credit for the AR-15, a company called ArmaLite did most of the heavy lifting.

ArmaLite Incorporated was established in 1954 as a subdivision of Fairchild Engine and Airplane Corporation. The original goal of the company was to incorporate cutting-edge materials like plastics and aluminum alloys into firearms designs.

The AR-1 Parasniper

The oldest child in the ArmaLite line was the AR-1 Parasniper (AR stands for “ArmaLite rifle,” not “assault rifle”). The lightweight, short-barreled AR-1 was made with foam-filled fiberglass furniture and an aluminum sleeve covering a steel-lined barrel. Although the AR-1 was ideal for soldiers jumping from perfectly good aircraft, the rifle saw little production.

The AR-5 and AR-7 Survival Rifles

Despite minimal production, the AR-1 drew some attention. As a result of the innovative design, ArmaLite was invited to enter a contest for an original aircrew survival rifle. Thus was born two different survival rifles: the AR-5, a lightweight bolt-action takedown rifle chambered for the .22 Hornet cartridge, and the AR-7, a weapon that disassembled and could be stored inside a floating stock. Both were adopted as survival weapons by the United States Air Force.

The AR-10

After the company’s successful survival rifle designs, ArmaLite received an invitation to compete for the US armed forces' new combat rifle. The winner would replace the M1 Garand.

With former Marine and Army Ordnance technician Eugene Stoner at the helm, ArmaLite developed the AR-10 as their contest entry.

The AR-10 was chambered in 7.62x51mm, had a lightweight receiver, and an integrated carrying handle. The most innovative feature of the AR-10 was actually the direct impingement system. This unique design channeled exhaust gases directly into the receiver to cycle the rifle’s bolt carrier. With this simplified design, ArmaLite reduced the overall weight of the weapon compared to similar rifles that used gas piston technology.

The AR-10 lost the contest to Springfield Armory’s T44, a design that would later become the M14. However, many elements of the AR-10 were reused in the smaller and lighter AR-15.

The Birth of the AR-15

Although the M14 was an adequate weapon, it had its shortcomings. Those shortcomings became highly evident in the jungles of Vietnam when pitted against the enemy’s AK-47s. Soldiers on the frontlines of the Vietnam conflict experienced regular problems controlling their M14s in fire mode.

The M14’s 7.62x51mm cartridges were also too heavy for American forces to carry enough ammo to achieve superior firepower over the Viet Cong.

Military officials attempted to remedy the situation by asking ArmaLite to develop a smaller version of the AR-10 chambered for the newer, lighter 5.56 NATO cartridges.

Dubbed the AR-15, the design was submitted for testing by the US Continental Army Command, with the hopes that these lightweight rifles could replace the Browning Automatic Rifle, M1 Garand, M1 Carbine, Thompson Submachine Gun, and M3 “Grease Gun” in one fell swoop.

Although the AR-15 performed well in every test category, Army Chief of Staff, General Maxwell Taylor, rejected the design in favor of the M14.

Meanwhile, ArmaLite fell on hard financial times and sold the rights to the AR-10 and AR-15 to Colt’s Manufacturing. Knowing a good firearms design when they saw it, Colt immediately began mass-producing the AR-15, which landed its first military contract with the Federation of Malaya (modern day Malaysia).

The AR-15 and the United States Military

In 1960, the AR-15 caught the attention of US Air Force Vice Chief of Staff, General Curtis LeMay. LeMay had the opportunity to bust watermelons off of fence posts with an AR-15 at an Independence Day picnic. He became an instant fan of the rifle’s accuracy and easy handling.

LeMay immediately ordered 8,500 AR-15s for his Air Force pilots, providing them a fighting chance should they be shot down over dangerous enemy territory.

In 1961, following his promotion to USAF Chief of Staff, LeMay ordered another 80,000 AR-15s. He contended that the AR-15’s lighter weight, recoil, and ammunition made it more effective than the bulky and burdensome M14.

A Conspiracy Theory?

While the AR-15 easily won over the United States Air Force, the Army was much harder to convince.

Army stats from that time showed 43% of shooters who used the AR-15 qualified Expert in marksmanship trials. In contrast, only 22% qualified Expert with the M14.

Although it seemed evident the AR-15 was more accurate and effective than the M14,military officials continued to veto the weapon’s use on the battlefield. General Maxwell Taylor, the Chair of the Joint Chiefs of Staff, continuously rejected the AR-15, claiming the military could not have two rifles chambered for different rounds at the same time.

While the AR-15 dealt with rejection, the AK-47 continued to dominate the U.S.-issued M14 in Vietnam.

In a strange twist of fate, Army Special Forces acquired several AR-15s; Soldiers sent back glowing reviews. Those positive reports inspired more testing, pitting the AR-15 against the AK-47 and M14.

The results of the testing were surprising. Despite the weapon’s stellar performance on the battlefield, the M14 continued to outperform in testing environments. Since test results didn’t support first-hand accounts from Special Forces, an investigation into testing procedures was ordered by Secretary of Defense Robert McNamara.

The ensuing investigation quickly discovered that Army Materiel Command (AMC) had rigged testing to favor the M14. For example, accuracy tests pitted the M14 in semi-auto against the AR-15 in automatic mode. AMC also selected straight-from-the-factory AR-15s to compete with match-grade M14s. Testing was obviously biased.

In January 1963, Secretary McNamara ordered a halt to the production of the M14. Colt stepped up to the plate with its massive manufacturing capabilities and began supplying AR-15s to all branches of the United States military.

After a few modifications (including the addition of a manual bolt closure), the rifle was re-designated as the M16. Today, the M16 reigns as the longest continuously serving military rifle in US history.

The Civilian AR-15

Although nearly identical in appearance, the civilian AR-15 has several key differences from the military M16. The hammer and trigger mechanisms are different designs. Also, the bolt carrier and internal lower receiver of the semi-auto AR-15 are milled differently than the automatic M16. This means the firing mechanisms of these two rifles are not interchangeable.

Civilian AR-15s also lack the three-round burst and automatic settings found on the M16.

AR-15 Variants

In September 2019, Colt announced it would cease AR-15 production for civilian use.

Although the AR-15 trademark is still registered to Colt, AR15-style rifles continue to be manufactured by numerous companies. For legal reasons, these “clones” are marketed under different names, although they retain the basic AR-15 design.

Today, “AR-15” is a sort of umbrella term rather than a brand name.

The modular design certainly contributes to the rifle’s popularity. Upper receivers can easily be swapped, creating virtually endless combinations of barrel lengths, twist rates, weights, and calibers. Aftermarket support also allows gun owners to customize their weapons with different stocks, triggers, handguards, and more.

The AR-15’s design allows the shooter to completely customize his (or her) weapon to meet the demands of any application. If you want to create a truly personalized weapon, the AR-15 is the perfect place to start.