THE DIFFERENCE BETWEEN AN AR15 AND AR10

Posted by Kris Vermillion on 25 days ago
THE DIFFERENCE BETWEEN AN AR15 AND AR10

The Difference Between an AR-15 and AR-10

It is this author’s opinion that the greatest takeaway from the history of the AR platform is that it was born and bred in Hollywood, CA. Oh, sweet, sweet irony.

Imagine being born in a town that makes BILLIONS of dollars by exploiting you but also thinks you should be illegal. Weird.

But that’s not why you’re here. You’re here to learn the difference between an AR-10 and an AR-15 rifle, and I’m here to help.

This article will cover the unique features that set the AR-10 and AR-15 apart as well as the similarities that keep them forever intertwined.

It’s easy to confuse the AR-15 and the AR-10 because to the average person (that’s me), they look exactly the same. They use the same style receivers constructed from the same material complimented by the same mechanisms that are manipulated in the same way. That’s a lot of “the same”.

And although the differences are subtle, they are also significant.

Let’s start with a broad overview.

The easiest way to tell the difference is to take a look as the magazine well (commonly called the magwell).This is the easiest and most obvious way to tell if you're looking at an AR15 or an AR10. The AR-10 magwell is just a bit bigger than the AR-15.

The AR-15 magazine well internal dimensions are approximately 2.4” x 0.9” with the AR-15 magazine being sized to function with cartridges with up to 2.26” overall length*.

The AR-10 magazine well internal dimensions are approximately 2.96” x 1.16” with the AR-10 magazine being sized to function with cartridges with up to 2.83” overall length*.

(*Overall length measurements here are industry standard and may vary slightly based on specific magazines).

Outside of the magwell size, the two platforms look nearly identical, but there are some significant differences.

Things that are different: The caliber, the size of the receivers, the magwell, the bolt catch, the mag release, the pivot pin, the hand guard size, the barrel nut, the bolt carrier group (see above), the charging handle the buffer tube, the buffer.

Things that are the same: The trigger, the safety, the buttstock, the pistol grip the castle nut.

To be clear, all of the items look the same and are really only different in their dimensions. The components perform the same features in each gun, but they have to be built to different parameters.

Both rifles are built on the same basic design that was born in the labs of ArmaLite in the 1950s in Hollywood, CA. At that time, ArmaLite was a small engineering outfit with less than ten employees, but by 1954 the US Air Force had already adopted one ArmaLite design: the AR-5. The AR-5 was/is a bolt-action .22 Hornet rifle designed as a life-saving/survival rifle for pilots to tuck into the tight space of a cockpit. Its greatest advantage was the ability to break down and then store all working components inside of the buttstock. In the broken down configuration the rifle was airtight and able to float. A perfect setup for combat pilots.

AR-10 History

In 1955 & 56, the US Army was looking to replace the M1 Garand at the go-to battle rifle for the American soldier. ArmaLite’s Chief Engineer was Eugene Stoner who was now faced with the task of offering the military an alternative to the M1 Garand - a 10 pound behemoth that held just eight rounds of 30-06 ammunition, but had been dubbed by General George S. Patton as the “greatest battle implement ever devised.”

Armalite was breaking new ground by using lightweight materials such as fiberglass and aluminum in its designs, and with the success of his AR-5 survival rifle design, Chief Engineer Eugene Stoner had experience in matching the military’s needs with a unique design. In working to win the contract to replace the M1, Stoner would eventually offer a rifle designed to hold twenty rounds of 7.62x51 and weigh less than eight pounds.That rifle would become known as the AR10.

AR-10 Design & Capabilities

The AR-10 had a Waffle Patterned Magazine and a charging device that looked like an upside-down trigger that ran through a channel cut through the top of the upper receiver. A “carry handle” helped cover the charging handle while giving a place for the rear sight to be seated.

ArmaLite presented the AR-10 as the “world’s most advanced combat rifle” due to its light weight, its highly effective caliber, and its ability to fire rifle grenades with no adjustment being necessary to the rifle itself. The user would drop a rifle grenade stem first into the muzzle of the rifle and then use grenade-propelling rounds in the issued magazine to launch the grenade. Pretty impressive.

The barrel was a steel composite wrapped in aluminum and the cylindrical design of the bolt carrier group was said to allow the higher pressure of the 7.62 x 51 round to be manageable due to the dispersion of the gas evenly along the length of the rifle’s lightweight body. Corrosion resistant material, ease of assembly and interchangeable parts reduced the service and maintenance of the AR10 to an “absolute minimum.” ArmaLite also boasted that the AR-10 was able to function longer than any other rifle without cleaning or lubrication.

From the barrel to the stock, the rifle was composed mainly of alloys and plastic which required a design that would unfortunately fail during military testing.

The US military refused the AR10 when an early submission had a round explode the barrel. Refusing the AR-10 from ArmaLite meant The Springfield T44 would win the contract and become known as the M-14, adopted for use in 1957. Stoner himself would later suggest that the loss to Springfield was more about politics than anything else.

However, ArmaLite did win contracts for the AR10 with Cuba, the Republic of the Sudan and Portugal soon thereafter. But ArmaLite wasn’t really keen on mass production. That’s why the earliest AR-10 rifles were mostly produced in the Netherlands. Forgotten Weapons has a fantastic piece on the evolution of AR-10 production if you really want to geek out on it.

AR-15 History

Throughout the Korean War American soldiers began to find that weight, rate of fire and range of effectiveness were top priorities that needed to be addressed in the military’s next battle rifle. In Korea, 600,000 Chinese fighters lost their lives. The Chinese soldiers were notorious for their hard charges up hills and across the battle field, and it was not uncommon for thousands of Chinese soldiers to attack an American position simultaneously.

The American soldier in Korea was outfitted with a heavy M1 Garand rifle that weighed almost ten pounds, held a mere 8 rounds and had a firing rate of about 50 rounds per minute. Imagine thousands of enemy fighters charging your location and you have only eight rounds at the ready. Sounds like a bad idea.

The AR-15 was designed to address these concerns. The rifle was lighter overall (weighing around five pounds) and used a smaller caliber round (.22) which not only reduced weight, it also added to the combat effectiveness of the weapon. Eugene Stoner said,

“There is the advantage that a small or light bullet has over a heavy one when it comes to wound ballistics. … What it amounts to is the fact that bullets are stabilized to fly through the air, and not through water, or a body, which is approximately the same density as the water. And they are stable as long as they are in the air. When they hit something, they immediately go unstable. … If you are talking about .30-caliber [like a bullet used in the M-14], this might remain stable through a human body. … While a little bullet, being it has a low mass, it senses an instability situation faster and reacts much faster. … this is what makes a little bullet pay off so much in wound ballistics.”

The reduction in weight would allow the American soldier’s combat load to not only get lighter but to also provide that soldier better defense capabilities due to the increased amount of ammunition he could carry. Despite those advantages, the US Military initially refused to sign on to the idea of the AR-15.

Who you ask determines the answer you will receive as to why.

What is known for sure is that the AR-15 initially performed poorly during testing which prompted Eugene Stone to personally fly out and evaluate the issues. Stoner determined that military armorer’s had altered parts of the rifle in ways that rendered it inoperable or ineffective. However, he was unable to convince the higher-ups at the time that his findings were the cause of the issues.

The ArmaLite & Colt Firearms Deal

In 1959, just a few short years after losing its bid to replace the M1 Garand, ArmaLite inked a deal with Colt Firearms to sell Colt the design for both the AR-10 and the AR-15. Colt was then able to sell early editions of the AR-15 to what was then called the Federation of Malaya (now known as Malaysia).

At the same time the conflict in Vietnam was escalating. There were several hundred American advisers in Vietnam, but no combat roles being taken on by US troops. Once Army Rangers actually began assisting in Vietnam, the AR-15 was acquired for testing in their battle arena and was met with rave reviews from the Rangers.

President Kennedy’s Secretary of Defense, Robert McNamara, turned the tide for the AR-15. McNamara wanted one rifle to cover all branches of the military. He viewed mass production as a way to control quality while keeping price down. The military ultimately adopted the AR-15 which would be the M16-A1 rifle put into service in Vietnam in 1965.

The Problematic Start for the M16-A1

The M16 went into full production in Colt’s facility with 45,000 guns rolling off the assembly line every month at its peak. However, the initial implementation of the M16-A1 was a failure by most accounts.

There were early problems of malfunctions reported in the field, and one soldier even penned a letter to his Senator saying he had seen American soldiers die because their rifles were failing during battle. That soldier’s Senator was Gaylord Nelson of Wisconsin who made the letter public. The letter prompted Congressman Richard Ichord of Missouri to begin an investigation of the rifle and its failures. One of the most notable findings was that in the initial testing of the rifle, the ammunition used was loaded with stick powder, but the military switched to ball powder for the issued ammunition. Ball powder is not only exponentially dirtier, it is also negatively affected by exposure to moisture. If the ammunition was exposed to moisture, it would swell and cause rounds to become lodged in the chamber. Soldiers in Vietnam learned quickly that they could not leave a round in the chamber for extended periods of time. Soldiers would have to unload their rifles before sleeping to keep the rifle from becoming jammed up by a swollen round (a result of the constant moisture in the air of the tropical jungles of Vietnam.)

Adding to the list of bad ideas from the government, the military told the soldiers that the rifles were self-cleaning and then issued the rifles without cleaning kits. Dirty barrels, bolt carrier groups and poor ammunition all created a deadly recipe for the American soldier on the battle field. One other important element is that the Department of Defense actually regressed the American soldier’s weapon in a sense by denying requests from the military to chrome plate the chamber of the M16. Once cleaning kits, proper ammunition and retrofitted chrome plated chambers were in place, the failure rate of the M16 fell drastically.

Today, in its many forms and variations, the AR-15 rightfully stands as America’s favorite rifle platform, providing both sport and security to the American civilian and the American soldier. Eugene Stoner’s design and the respective efforts of ArmaLite and Colt to bring it to fruition continue to play a pivotal role in providing liberty and safety to oppressed and endangered people around the world.

What Calibers are the AR15 and AR10?

Both the AR15 and AR10 are capable of housing multiple calibers.

Here is a non-exhaustive list of the separate but equally impressive capabilities of the two.

About Kris Vermillion

About Kris Vermillion

Kris Vermillion is a lifelong shooter who focuses his training on defensive shooting techniques and the shooter’s mindset. Kris works with the Palmetto State Armory E-Commerce and Marketing teams.

Dan 20 days ago at 11:16 AM
Thank you for shearing, great info and history
John Wheatman 20 days ago at 11:52 PM
Fantastic read. Thanks Kris.
Todd Pruett 11 days ago at 2:49 PM
Very informative article. Learned a few new things especially about the problems in the beginning stages.
Jon R Tatum 10 days ago at 12:25 PM
Great article, interesting history, lots of good information. Thank You