While most shooters and many non-shooters are familiar with the famous AR-15 rifle, many people are not familiar with the AR-10 rifle. However, the AR-10 rifle is actually the predecessor to the AR-15 and was originally designed to replace the venerable M-1 Garand service rifle. However, despite the fact that the AR-15 and AR-10 have a very similar appearance, there are significant differences between the two that are an intentional part of their design. Consequently, although both the AR-10 and AR-15 have a similar appearance and employ the same action, they are actually designed for entirely different purposes.

A Short History Lesson

For instance, while the Armalite Rifle Model 10 (aka AR-10) was “the best lightweight automatic rifle ever tested by the Armory” according to Springfield Armory staff who tested the AR-10 during the U.S. Army’s Lightweight Rifle Program in the late 1950’s, it was specifically designed to replace the M-1 Garand as mentioned above. Therefore, it was designed to fire a shortened version of the U.S. Military .30-06 Springfield cartridge (aka 7.62 x 63mm) designated as the 7.62 x 51mm NATO cartridge.

However, while this new cartridge was an excellent choice for firing at targets at extended ranges as well as for firing at hardened targets, it required a relatively large upper receiver, bolt carrier assembly, lower receiver, and magazine. Therefore, the AR-10 was a bit too bulky, too heavy, and too powerful for infantry engagements at 300 yards or less which were becoming increasingly more common in modern warfare.

Consequently, the U.S. Continental Army Command (CONARC) invited Eugene Stoner (who by this time had left Armalite and now worked for Colt) to design a scaled down version of his AR-10 rifle which, although it had not been chosen to replace the M-1 Garand, was not forgotten.

What set the AR-10 Apart?

So, what made the AR-10 so memorable during the Lightweight Rifle Trials conducted in the late 1950’s by the U.S. Army that it was chosen as the basis for the army’s new service rifle? Designed by Eugene Stoner while working for Armalite in the late 1950’s, Stoner used the experience he gained working for Vega Aircraft Company combined with his experience as a U.S. Marine Corps Ordinance soldier prior to his employment at Armalite to design the lightest battle rifle in the world.

Taking what was then a unique approach to firearms design, Stoner combined steel, aircraft grade aluminum, and glass reinforced plastic (aka fiberglass) components to create a selective fire (aka fully automatic) service rifle that weighed a mere 6.85 pounds compared to the M1 Garand which weighed 9.5 pounds.

Furthermore, Stoner’s rifle featured an adjustable, direct impingement, gas system, a straight-line stock with an internal recoil compensator, a detachable box magazine, rugged, elevated, sights and, an oversized aluminum flash suppressor. In other words, the AR-10 was an infantry man’s dream rifle!

Thus, when invited by CONARC to scale down his AR-10, Stoner migrated many of these design innovations to his design of the AR-15 to create a rifle which was chambered for the military’s new Small Caliber High Velocity round; the 5.56 x 45mm NATO cartridge.

The AR-10 vs. AR-15

So, if the AR-10 and the AR-15 have the same appearance and use the same type of direct gas impingement system to cycle the action, then what is the difference between the two? Well, if you were to view both rifles side by side, you would immediately notice the difference in their respective sizes.

Although both rifles have a very similar barrel length at 21 inches for the AR-10 and 20 inches for the AR-15 and a similar overall length of 42 inches for the AR-10 and 39 inches for the AR-15 (depending on barrel length and LOP), both the upper and lower receivers of the AR-10, as well as its detachable magazine, are significantly larger than those of the AR-15 in order to accommodate the longer, more powerful, cartridge fired by the AR-10. Therefore, the AR-10 has the appearance of being a significantly larger rifle than the AR-15.

Furthermore, the AR-10 commonly weighs anywhere from 7 to 9 pounds (without attachments) depending on how it is configured whereas, the AR-15 commonly weighs between 6 and 7 1/2 pounds depending on its configuration.

Consequently, many shooters prefer the AR-15 over the AR-10 due to its smaller size and its lighter weight as well as the lack of recoil generated by its significantly smaller cartridge. Thus, the AR-15 is most often chosen for recreational shooting (aka plinking), competition action shooting, medium sized game hunting, and home defense. However, the AR-10 is more often the choice of large game hunters and long range target shooters due the fact that it fires a significantly larger, more powerful, cartridge with a larger diameter bullet than the AR-15 does.

However, the fun doesn’t stop there because both the AR-10 and the AR-15 can be converted to fire a plethora of specialty and wildcat cartridges such as the 6.8mm SPC, the .300 Blackout, and the .50 Beowulf simply by changing the upper receiver assembly and the magazine. So, regardless of your intended purpose, if the standard 5.56mm or 7.62mm NATO cartridges don’t meet your needs, then chances are that there is a specialty or wildcat cartridge that does.

7.62 x 51mm NATO vs. 5.56 x 45mm NATO

Speaking of standard cartridges, what is the difference between the standard AR-10 cartridge and the standard AR-15 cartridge? Of course, when we refer to standard cartridges for the AR-10 and the AR-15, we are referring to the standard NATO military cartridges which consist of two center fire, bottle neck, rifle cartridges which measure 7.62 x 51mm and 5.56 x 45mm respectively or, .30 and .22 caliber with case lengths of 2.015 inches and 1.760 inches each.

In addition to their vastly different case lengths and case capacities, the two cartridges also have drastically different muzzle velocities. For instance, the AR-10, which is designed to fire the 7.62 x 51mm NATO cartridge (aka .308 Winchester) has a muzzle velocity of 2,800 fps when firing the 147 grain M80 FMJ NATO round while the AR-15 has a muzzle velocity of 3,150 fps when firing the 62 grain M855A1 FMJBT NATO round.

However, despite the significantly faster muzzle velocity of the AR-15 round, the AR-10 round produces far more kinetic energy. For instance, the AR-10 147 grain M80 FMJ NATO round produces a whopping 2,559 ft-lb of kinetic energy whereas, the AR-15 62 grain M855A1 FMJBT NATO round produces a mere 1,371 ft-lb of kinetic energy.

Thus, although the AR-10 does produce noticeably more recoil than the AR-15, it also produces significantly more muzzle velocity and more kinetic energy and thus, the AR-10 is capable of shooting over longer ranges, penetrating harder targets, and harvesting large game species than the AR-15 is. But, it’s also longer, heavier, and more difficult to maneuver quickly than the AR-15.

So, as you can see, the AR-10 and the AR-15 both have significant differences that translate to significant advantages and disadvantages over the other which, in turn, tend to dictate which one a shooter chooses depending on their intended purpose.

Last, if you would like to try your hand at building your own AR-15 or AR-10 rifle using an 80 percent lower receiver, then you can find everything you need to assemble a complete rifle at American Made Tactical including 80 percent complete lower receivers, lower receiver parts kits, and complete upper receiver assemblies. Plus, completing and assembling your own rifle can be easily accomplished at home with simple tools and thus, most any shooter can do it safely and legally.