Let’s face it: getting an AR rifle in .223/5.56 is BORING. It’s too easy! Everyone has one. It shows a lack of imagination.
Oh, okay, fine. .223 and 5.56 NATO has their virtues. It’s cheap, which means you can do a lot more shooting than with other chamberings. It’s proven in self-defense capacities, too. If you want to shoot a rifle in something other than .22 LR, but aren’t going to be doing a lot of hunting, it’s a good choice.
But what if you aspire to something besides the same ‘ol, same ‘ol?
Here are three AR rifle chamberings to look at if you want to do more than just punch paper. I’m leaving some details out for brevity; I could devote an entire article to each one of these cartridges on their own. If there’s something you think I missed, put it in the comments.
The .300 BLK round — also known as .300 AAC Blackout or .300 Blackout — is another good choice in an intermediate caliber. The round was made by necking a .223 Remington up to accept a .308-caliber bullet. It’s basically just like the .300 Whisper, except it’s commercially successful. This gives the round certain advantages…but certain disadvantages too.
The .300 BLK was created to serve several needs. First, it had to fit the standard AR-15 action, so carrying capacity isn’t limited as it is with the AR-10. Second, it had to use a .30 caliber bullet to give it a bit more wallop, similar to 7.62x39mm.
Finally, it had to function without issues when the rifle is suppressed and/or when subsonic ammunition is used, as the M4 system functions best above a certain pressure threshold.
Obviously, that gives the round certain advantages for a special forces operator (makes a good close-quarters long gun) and for the recoil-conscious modern shooter who uses a suppressor. For handloaders, the round uses .308 projectiles, which basically means the world is your oyster so long as you stay within approved pressure levels.
Available bullet weights range from light varmint loads around 78 grains up to 220 grains. Velocities, depending on the load, can be anywhere from 1,000 to 3,000 fps from the muzzle, and energy can be 500 ft-lbs to just under 1,400 ft-lbs.
It’s great for plinking. It’s great for self-defense, and you can hunt with it, but it’s limited to shorter ranges. It makes an excellent cartridge for hogs or Eastern whitetails (we grow ’em bigger on the Left Coast) in heavily-wooded areas.
In other words, it’s a tactical .30-30. Nothing wrong with that!
If you want even more of a wallop, there’s the .458 SOCOM.
The .458 SOCOM – in addition to the .450 Bushmaster, which is the .45 Professional wildcat with a haircut – was designed to put a big bore bullet in a small case that will fit in a standard AR-15 frame.
The legend goes that some military personnel found that Somali fighters (during the Mogadishu campaign) weren’t as effectively deterred by 5.56 because they chewed khat. Khat is a plant, the leaves of which contain cathinone, an alkaloid with similar properties to cocaine. So, the cartridge was designed by Marty ter Weeme of Teppo Jutsu.
If your day is done, and you want to ride on, cathinone…eh. Doesn’t work. Anyway . . .
The difference between the two is that .458 SOCOM is a necked-up .50 AE case, with a .458-in projectile. By contrast, .450 BM is a necked-up .284 Winchester with a .452-inch projectile, the same as .45 ACP, .45 Colt and .45-70 Gov’t.
Both operate at less than 40,000 psi of chamber pressure, both are used with similar bullet weights (250 grains and up) and both achieve similar velocities and muzzle energies.
Velocity and energy ranges by bullet weight and load, ranging from around 2,100 fps and 2500 ft-lbs with a 250-gr. projectile to around 1,000 fps and 1300 ft-lbs with a 600-gr. projectile. If you love the AR platform, but want to put a BIG HOLE in something…this is the ticket. There are some caveats, though.
First, it’s expensive. Second, capacity is drastically reduced compared to .223, in that magazines need to be single-stack due to the size of the round. A 20-round magazine for .223 holds 7 rounds of .458, a 30-rounder holds 10. Third, forget long-range.
Just like .300 BLK, though, .458 makes a great self-defense gun. It also makes a great hunting round for short-range; with a suitable bullet, it could take any game in North America. Unfortunately, it appears that .458 SOCOM hasn’t been approved for straight-wall jurisdictions…though .450 Bushmaster is.
Basically, you could think of .458 SOCOM as a high-tech .45-70.
Lastly, we come to 6.8 SPC. The 6.8mm Remington Special Purpose Cartridge was developed for Armed Forces testing.
They had the idea that the 5.56mm was lacking at longer ranges, and also that the 6mm family had a lot of potential for use as a sniper cartridge given its great accuracy and lower recoil than .30-caliber rounds such as 7.62x51mm and .300 Winchester Magnum.
The US Army Marksmanship Unit did some toying around, eventually arriving at a 6.8mm bullet as having the best attributes, and got Remington to cook up the ammo. The idea stuck, as the Armed Forces are purportedly going to switch to a 6.5mm or 6.8mm cartridge as their standard round sometime in the near future.
This is, of course, a modern take on a very old idea.
Remington and Winchester cooked up cartridges with the same design ethos (put smaller bullet in case, bullet go faster and farther) which led to the 7mm Remington Magnum and the .270 Winchester, among many others (like the .25-06, .280 Remington, .257 Roberts, ad inifinitum) one could name. Gun writers like Warren Page and Jack O’Connor certainly helped sell them.
Obviously, it had to be adapted to the AR-15 platform, so Remington trimmed the obscure .30 Remington (basically a .30-30 for non-lever-action rifles) down and inserted a 6.8mm bullet (.270 caliber in case you’re curious; like I said, it’s just a tactical variation on an established theme) in the case. Overall length is 2.26 inches, the same as .223 Remington/5.56mm.
However, it isn’t a tactical .270, and the reason why is the shorter case. You see, .270 Winchester has a case length of 2.54 inches vs 1.667 inches for the 6.8 SPC, so the heavier bullets (120 grains and up) are too long to seat in the case. Thus, cartridges are limited to about 115 grains in most factory loadings.
That said, the 6.8 SPC entered field testing with the armed forces, and with very positive results. While it has less muzzle velocity than 5.56, it makes up for it with a higher ballistic coefficient, so a 110-grain 6.8mm SPC bullet has the same velocity at 400 yards as a 55-grain 5.56 M193 round does at the same distance despite leaving the muzzle at 400 fewer feet per second and also carrying 400 more ft-lbs of energy.
It was also found to still be effective at close and moderately longer distances (say out to 600 yards) from carbine and SBR barrel lengths, and quite controllable in full-auto. In short, a jack of all trades that’s quite decent.
In the civilian realm, it’s found adoption with folks who hunt with an AR-platform rifle but not at uber-long ranges.
If you wanted an intermediate cartridge that had more punch than .223, and longer legs, but didn’t want to go whole-hog on an AR-10…this would be the ticket. Basically it’s a tactical .270, though without the same breadth of capability of one. Then again, most people who buy one aren’t going to be hunting, so who cares?
What about you? Is there a different alternative AR rifle cartridge that you’re more interested in? Tell us about it in the comments.