300 Blackout and .308 are wildly different cartridges by nearly every measure – however, because both rounds have become so popular in the AR platform, it’s only fitting that we break down the differences and compare their performance and application. Each cartridge boasts different loads and grain counts, so we’ll take a look at the most common, “average” .308 (168-grain), and we’ll look at both supersonic and subsonic 300 Blackout loads for a proper comparison.
300 Blackout and .308 Winchester by The Numbers
Before we break down their benefits, drawbacks and applications, we need to look at each round’s size, ballistics, grain counts and general data:
- Weight (average): 168 grains
- Velocity (average): 2,650 ft/s
- Energy (average): 2,700 lb.-ft.
300 AAC Blackout:
- Weight (average): Supersonic, 125 grain, Subsonic, 220 grains
- Velocity (average): Supersonic, 2,215 ft/s, Subsonic, 1,010 ft/s
- Energy (average): Supersonic, 1,350 lb.-ft., Subsonic, 500 lb.-ft.
What a .308 AR is Good For:
The .308 cartridge was developed and introduced in 1952, just two years before NATO adopted it as 7.62x51mm NATO T65. The original intent of the cartridge was to function a commercial hunting round, and today it remains the most popular short-action, big-game hunting round on Earth. Although today’s .308 cartridge is technically different than NATO’s 7.62×51, their interchangeability is considered safe.
Any AR platform that cycles .308 is generally referred to as an AR 10. So why might you want one? Simply put, the AR 10 is the everyman’s bench rifle and semiautomatic long gun. It provides good, reliable long-range ballistics that can produce thousand-yard groups, it offers plenty of punch with relatively moderate recoil. For its performance, it’s a generally inexpensive round to shoot.
The AR 10 is great for long range hunting and target shooting, but it is generally a heavy gun. Unlike 300 Blackout uppers, the AR 10 upper needs a different AR lower with a bigger bolt carrier group and trigger assembly. And don’t even think about turning an AR 10 into a pistol – the ballistics and recoil are nearly unmanageable. To be sure, this is a long-range rifle round and nothing else. Many invest in an AR 10 because they already own a bolt gun that shoots .308.
What a 300 Blackout AR 15 is Good For:
The answer to that question is easy: Damn near everything. Supersonic 300 Blackout loads pack enough punch that they outmatch any 5.56 load by a few hundred lb.-ft., while subsonic loads hit with enough force, suppressed, that they’ll take down a large hog without hesitation. The ballistic difference between the common M855, 62-grain 5.56 and 110-grain 300 Blackout is so marginal that both rounds performance effectively the same beyond 400 yards.
But what’s best part about 300 Blackout? Quiet shooting with the utmost ease, of course. Where other rifles need a different gas system, bolt carrier, buffer and barrel to go from unsuppressed to suppressed, all you need is a magazine swap and a can to thread to your muzzle. 300 Blackout suppresses easily without any modifications to your rifle, so you can go from shooting far out with 110-grain to up close and quiet with 220-grain in a matter of seconds. The 300 Blackout is a versatile round that even makes for a good AR pistol cartridge.