Black Rifles & Tactical Guns

CCW Weekend: .300 BLK vs 5.56 In Your AR Pistol Or SBR – A Brief Overview


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By Sam Hoober, Alien Gear Holsters

A whole bunch of people are snatching up AR-style rifles, carbines, SBRs and AR pistols and in record numbers. This leads also to the practical question of whether you should get yours chambered in .300 BLK, aka .300 AAC Blackout, or in 5.56mm NATO-cum-.223 Remington.

It’s a good practical consideration for your home defense gun, or for those gullible enough to think a truck gun is a good idea because it’s just not (because you won’t get to it in time, genius) and that’s the kind of gun people buy for one.

The short answer? .300 BLK or a pistol-caliber PCC in 9mm or .45 ACP; leave 5.56mm for carbines and rifles.

The slightly longer answer? Since 5.56mm terminal performance is far more velocity-based, you’re better off with .300 BLK or a pistol caliber AR pistol or SBR since those cartridges were designed with shorter barrels in mind.

Bear in mind that this topic has a lot of ins, outs and what-have-yous.

Some people might bring up something about long range, and I’m going to stop you right there. You don’t buy a gun with a short barrel to shoot at long range. If you want long range capability that’s still usable for CQB, get a carbine not an AR pistol or SBR and that’s the end of it.

So, let’s flesh this out a little bit more.

The .223 Remington cartridge and its NATO-ified brother, 5.56x45mm NATO, were developed from the .222 Remington cartridge. The .222 Remington is a varmint cartridge, through and through and so, really, is the .223.

It’s just that .223/5.56mm was discovered to be very effective on human targets in the bargain as well as being very easy to shoot.

If you aren’t aware, here’s the gist of varmint targets: make light bullet go very fast and not drop too much. Easy to shoot, and therefore easy to shoot accurately out to longer distances.

What was noticed about .223/5.56mm was that it had a beneficial (for the shooter, anyway) effect of fragmenting inside fleshy targets, so it had very effective terminal performance for such a small bullet.

Why is that important?

For a varmint cartridge to be effective, it has to travel fast. Velocity was the selling point for varmint rounds like .220 Swift and .22-250 Remington, both of which reached 4000 fps+ in the 40 gr loadings.

Common 55-gr projectiles reach speeds of 3200+ fps from a 20-inch (plus) barrel in .223 Remington. High velocity, therefore, is key to high speed/low weight calibers for optimal efficacy.

And what, pray tell, produces velocity?

Partially it’s powder charge, but the real deciding factor is barrel length. The longer the barrel, the more pressure can build up behind it and the faster the bullet will leave the muzzle.

The gist here is that 5.56mm is best-suited for a carbine- or rifle-length barrel for terminal performance. Since terminal performance must-needs be a concern for personal defense, which means an SBR or AR pistol in 5.56mm is not the best platform for that cartridge.

The magic number varies by sources, but the golden number for 55-gr projectiles appears to be around 2600 to 2700 fps. From a carbine-length (16- to 16.5-inch) barrel, 55-gr 5.56mm drops to 2600 fps around 160ish meters.

It’s like having a lightweight hunting rifle in .338 Win Mag. Oh you could do it, but it’s going to beat you like the redheaded stepchild of a rented mule that owed you money.

Let us then consider .300 AAC Blackout.

.300 AAC Blackout was developed by the Advanced Armament Corporation specifically to do the following:

Fit in an AR-15 magazine, which it does. Fewer of them than 5.56mm, but they do, and therefore it chambers, fires and otherwise operates just fine in any mini-action platform.

It was also made so terminal performance didn’t suffer with shorter barrel length or when a suppressor was used on the rifle, as well as deliver more muzzle energy than 5.56mm.

The .300 BLK was developed for use by military units that specialized in clandestine CQB operations, and needed to run well in short-barreled rifles with suppressors without loss of efficacy, and therefore to work better at short range.

In other words, it was literally made for SBR and AR pistol platforms.

Since then it has been co-opted into other applications, with some people using it for hunting though when taken out of its more defense-oriented original purpose and the .300 BLK basically becomes little more than .30-30 with a tactical vest and uglier rifles to boot.

That’s right; I said it. The Winchester ’94 is a prettier rifle than an AR and we all know it. Now quit your crying and if any of you in the comments section dares disagree, may the ghost of John Moses Browning rearrange your sock drawer.

Point being?

Terminal performance of .300 AAC Blackout is less velocity-dependent than 5.56mm and therefore a short-barrel platform is not only a good idea, the cartridge was literally made for it.

As to pistol-caliber AR pistols, these are probably the best bang for your buck.

Recoil will be drastically less than an AR pistol or SBR in 5.56mm or .300 BLK. Ammunition will be cheaper. That means it’s cheaper to shoot and easier to shoot in the bargain.

As to terminal performance?

Well, hollow point ammunition – just like fragmenting varmint ammunition – is likewise velocity based, and AR pistol PCCs tend to have longer barrels than actual handguns. That 9mm 115 gr JHP or 230-gr .45 ACP JHP will be traveling faster, hitting harder and expanding more reliably.

Granted, rifle calibers hit harder and cause far more damage when they hit fleshy targets. As Clint Smith is fond of saying, pistols put holes IN things and rifles put holes THROUGH things.

As to which to get, that’s up to you to decide for yourself, but if you’re getting a short-barreled AR- or AK-platform gun, those are the better choices for the platform.

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Sam Hoober is a Contributing Editor to, a subsidiary of Hayden, ID, based Tedder Industries, where he writes about gun accessories, gun safety, open and concealed carry tips. Click here to visit