The current state of the AR sporting rifle market is a mess. There, I said it. On the one hand, it seems like a golden age, with prices having plummeted, and a proliferation of enticing, purpose built cartridges to fill every shooting niche. On the other hand, it’s a mess. I noticed the beginning of the trend years ago.
It’s been well over a decade now since AR platform rifles stood on their collective tails like a squadron of F-15s and lit afterburners for a vertical climb that is just now sputtering out. During the intervening years new manufacturers entered the market every month, and new, alternative cartridges were added to stoke the fire. But it seems everyone from rifle makers to cartridge designers/ammunition manufacturers was so intent on grabbing a slice of pie, that a lot of important development details were overlooked.
Back before the market went nuts, when AR-15s came in as many flavors as Ford Model Ts, they developed a reputation for being Lego sets. The formula for making a .223/5.56 rifle run properly was well understood, and it was a near certainty that parts from reputable makers would result in a reliable build (though plenty of home gunsmiths muffed it, regardless).
But even then, the AR-10 platform hinted at the troubles to come. Many .308 chambered SR-25 pattern rifles were not so great. Gen 1 DPMS rifles, for instance, were dismally unreliable, despite that company’s long standing reputation as a respectable AR-15 maker. On the other hand, Armalite--related to the original AR-10 developer by name only--managed to produce outstanding large format rifles.
A pattern emerged as new cartridges were developed for ARs. Oftentimes, the original developer(s) got it right in their offering, while copycats failed more often than they succeeded. The .300 Whisper/Blackout craze offers great examples. The 6.8 SPC offered suffering to the unsuspecting. Alexander Arms’ 6.5 Grendels ran flawlessly, and while the cartridge’s popularity increased after going SAAMI, it is now easy to find examples that are not reliable.
Lots of problems surfaced when the 6.5mm craze bled over into the AR-10 format. Cartridges like the .260 Rem and its erstwhile usurper, the 6.5 Creedmoor, offered enticing ballistics, and in a hurry to hop on the rapidly accelerating bandwagon, a number of makers trotted out rifles in these chamberings. Many were unworthy. The AR as Lego set philosophy was an epic fail where alternative calibers were concerned, and many unsuspecting consumers paid the price.
The SA 6.5s are an interesting case study. I was an early adopter of 6.5 cartridges, so I’ve been studying their ballistics--both internal and external--for over a decade. Thing is, you don’t have to be an internal ballistics expert to understand that a .260 or Creedmoor is quite different than a .308 Win. The 6.5s use slower burning powder, which carry a longer, higher pressure curve through the bore. It astounds me that many AR makers assumed a .308 gas/buffer system would work just as well on a 6.5mm. But that’s exactly what happened.
Complicating matters more, 6.5s, with their skinny bullets, do not work well on .308 feed ramps. The ramps cut into the barrel extension are designed to guide, and lift a .308 cal bullet, so that as it nears the breech, it is elevated to the chamber mouth, ideally missing the breech feed cone entirely, thus avoiding deformation.
However, 6.5 bullets are narrow enough to go through the “teeth” of the feed ramp and hit the breech. A good barrel maker understands this, and will widen/deepen the breech feed cone to insure reliable feeding. Plenty of barrel makers do not, and will cut a standard, .308 feed cone, which ensures that 6.5 bullet tips will be badly deformed, assuming the cartridge makes it into the chamber at all. Despite the popularity of 6.5s these days, a thorough search failed to turn up any AR-10 barrel extension with feed ramps cut specifically for 6.5mm cartridges. Amazing, no?
The AR mess doesn’t end there. Magazine manufacturers are strangely complacent, preferring to stick to the safely trodden paths of .223 and .308, ignoring a host of new entries even when one becomes popular. In my excitement over my first Grendel, I bought a stack of magazines early on, all of which were reliable. Good luck finding a reliable Grendel mag now. The .450 bushmaster is growing in popularity, but no mag exists that will reliably feed more than a few rounds. Despite enormous popularity, mags for the .300 Blk are still hit or miss. Winchester seems unconcerned that no mag exists for its new .350 Legend.
Point is, there’s a disconnect, which is odd, as altering magazine designs to fit a different cartridge usually involves little more than changing internal guide rail dimensions. I have altered Lancers to reliably stack and feed 12rds of Bushmaster, and Pmags to feed 20rds of .36 RPP. It ain’t rocket science.
One last note. The Army’s adoption of the M4 helped popularize the carbine length gas system, but unless you’re building a SBR, short gas systems are best avoided. Carbine gas systems are more finicky, cycle more violently, and put more heat into the action. They are also tougher on brass. If you’re getting into a .308, stick with a rifle length system, and if you’re going with a 6.5, I highly recommend going with a magnum length (rifle +2”) gas system. Longer gas systems offer benefits with any cartridge, and there is really no down side unless you must have a very high cyclic rate. Most civilians do not.
This is the golden age of the AR, no question. But buyer beware, they are not Lego sets. If you are thinking of getting into a new caliber, do your homework and get educated about its potential pitfalls. Then contact reputable manufacturers to quiz them. If you can’t get someone on the phone who is willing and able to answer your technical concerns, move on. Experience with the caliber and excellent customer service are both paramount. If you are going to piece the rifle together, then go with the barrel maker’s recommendations regarding gas blocks, BCGs and buffers. Apart from that, go wild. Have fun. Be safe.
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Frequently Asked Questions
What is better an AR-10 or AR-15?
There isn’t much difference between an AR-10 or AR-15, other than the difference in caliber options resulting in a slightly heavier and larger rifle. Ultimately, a lot depends on your use of the rifle.
What is the effective range of an AR-10?
On an average, 400-600 yards is considered to be an effective range for the AR-10 rifle. Moreover, a lot depends on the weather conditions, shooter’s skillset and the conditions for the shot.
What is the largest AR-10 caliber?
Some of the largest AR-10 caliber rifles are the 6.5 Creedmoor, 7-mm-08 Remington, .358 Winchester, and . 338 Federal.