When Dr. Dave Dolbee and I discussed this article, the wheels in my mind were whirling. I have used each platform, find both to be great guns, and think everyone should own more than one of each. However, the how and why I came to this conclusion need to be explained.
As far as handling and ergonomics, each is brilliantly designed and the function is the same. Some new shooters may not realize that the AR-10 7.62x51mm rifle came first. This .308 rifle competed with the FN FAL and M14. In the end, the rifle was downsized into the .223 caliber AR-15.
The primary difference between the rifles is the caliber. The AR-10 is chambered for the .308 Winchester or 7.62x51mm NATO. The AR-15 chambers the .223 Remington or 5.56mm NATO cartridge. There are others, but the big ones, such as the .300 Short Magnum, must be chambered in the AR-10. The .308 replaced the .30-06 as a sniper and machine gun cartridge, and still serves today.
There are also many M14 rifles serving. The rifle has been referred to as shoulder-fired artillery overseas, compared to the .223. To the best of my knowledge, there are no AR-10s in military service. The .308 usually has a 1:11-inch twist; the .223 in modern rifles may feature a number of twists, but 1:8 seems most common. Both (usually) feature a 16-inch barrel.
The AR-15 was a response to the Russian AK-47 we encountered in Vietnam. The lighter AK was controllable in automatic fire and more ammunition could be carried than the M14 allowed, putting our soldiers at a disadvantage. President Kennedy ordered the AK-47 tested against the AR-15. The rifle was controversial and early versions suffered due to the powder combination used in the initial ammunition issued.
The rifle continued to serve and was developed into the present AR-15/M4 rifle. The new AR-10s are usually a 1.5 pounds heavier than the AR-15 and about three inches longer, due to the heavier receiver and longer stock. The AR-10 fires a stronger cartridge with more momentum, so you could not simply re-barrel the AR-15.
The bolt, bolt carrier, and springs must be heavier to accommodate the .308 Winchester. The AR-15 may accept a 20- or 30-round magazine, the AR-10 usually deploys a 20-round magazine. The decision is—do you wish to deploy a heavier rifle that is more powerful, or to maintain the AR-15 rifle—which is plenty powerful for most choices.
If you hunt medium game, the .308 is the better choice by far. It is effective against deer-sized animals well past 200 yards. You will get into a solid position and take the shot. If you are varmint hunting, the .223 AR-15 is the better choice. You may be firing more quickly in rapid movement. For personal and home defense, the AR-15 is the better choice based on ease of control and modest penetration in a home defense situation.
The .308 has greater wound potential, knockdown power, and penetration. At close range, the .223 is designed to fragment. A 55-grain bullet at 3,200 fps produces a tremendous wound. The problem, as velocity slows the rifle becomes less effective. The rule of thumb is the .223 loses much of its effectiveness at 100 to 125 yards. The .223 is very effective at close range with the proper loads, especially with multiple shots. The .223 will carry more ammunition for an equal weight. The .308 is the better choice for designated marksman rifles intended to be used past 100 yards.
When you get down to brass tacks, the difference between the two rifles boils down to caliber and the intended mission. The AR-10 is more powerful, heavier, and holds less ammunition. The AR-15 is lighter and holds more ammunition. Inside of 100 yards, the .223 is plenty effective on man-sized threats.
Ammunition is cheap and plentiful for the .223, and there are more ammo choices. For personal defense—9 times out of 10—the AR-15 is the better choice. For those living on the plains or needing a good hunting rifle that may double in the area defense role, the AR-10 is a great choice.
As for accuracy there are true tack drivers in either configuration. I have not fired a dog in either that I can recall. As far as reliability and functionality, this is more a product of the ammunition, how clean it burns, and shooter maintenance.
Effectiveness for Home and Area Defense
.223 loads expand or fragment, producing wounds that result in immediate cessation of hostile action. This makes for a safer load for home defense. The .308 may punch through a threat, while doing less damage. While there are modern, purpose-designed .308 loads that produce good wound ballistics, the .223 remains the load of choice at shorter range. The .308 is the long-range rifle.
There are interesting things going on in either variation. As an example, the .224 Valkyrie, as developed by Federal Cartridge Company, is giving AR-15 fans an option that may shooter flatter than the 6.5 Creedmoor. Time will tell which will be more popular in the future.
At present the AR-15 is far more numerous. The AR-10 has a loyal, but smaller, following. Carefully study your needs and choose well. There are well-made rifles among each type that serve a real purpose.
Do you prefer the AR-10 or AR-15 for personal defense? Which model is your favorite? Share your answers in the comment section.