The Best Caliber Not to Buy - 6mm ARC (Ballistic Advantage 16-inch SPR)

Updated 1 week ago

Good morning, everyone, this is John with, today we're going to be taking a look at a new setup for me in a very interesting caliber, that is 6mm ARC, as the title implies. This setup is from Ballistic Advantage, it's kind of a hodgepodge of parts that we will go over, mainly focusing on the barrel and the new cartridge now.

For those of you who don't know, the 6mm ARC was developed by Hornady as basically the pinnacle of performance that you can get in an AR-15 magazine, so the 6mm ARC is based off of I believe the 220 Russian, which is what the 7.62x39, that everyone loves, and the 6.5 Grendel is also made out of. With that 6mm projectile in the 6 ARC, in a relatively short fat case that does fit into an AR-15 magazine, you're getting a ton of performance in the least amount of space possible. The 6mm projectile in general is extremely popular in the PRS world, I believe it is the most popular PRS cartridge in a ton of different calibers and cartridges, dasher, GT, so on and so forth, for the PRS guys, but that's much more reload specific versus a factory 6mm ARC.
The ARC in general, this is a 103 Precision Hunter loads, this is actually a hunting load, I have a bunch of this, and then some 105 Hornady Black. Unfortunately, as we'll get into a little bit later on, the ammunition can be difficult to source and a little bit on the pricey side, but the main advantage of 6mm ARC is that it runs with relatively few quirks in an AR-15 package. The 6mm ARC is by no means the hottest best performing 6mm cartridge out there, there are a ton of hotter cartridges out there.

One of the side effects of having a 6mm bullet in a smaller cases that you are going to get a little bit reduced velocities versus other 6mm loadings, but you get a ton of performance in an AR-15. What that means is you can get a 7-pound based rifle that out of the box can hit a thousand yards fairly easily with very minimal recoil, meaning that you get a very lightweight package AR-15 size, not AR-10, DPMS or some of those hybrid designs, you can get a true 7-pound rifle or even sub seven pound rifle in some cases and get that exceptional mid to long range performance.

In this configuration, this is a 16-inch 6mm ARC, which is definitely in the middle of the road for 6mm ARC barrel lengths, this is not quite the lightest setup as it is definitely a little bit more accuracy focused as I knew I was going to be doing a little bit more distanceshooting with it than I would like a normal AR-15 setup. The barrel that is in here, this is one of Ballistic Advantage’s 16-inch 6mm ARC, this is the one of their premium black barrel, so it is a nitrated 416R stainless steel barrel, and this is in their SPR profile. The SPR profile is a copy of the Mark 12 profile, the Mark 12, if you're somehow not aware, is a heavy barrel 556, this is the same profile barrel, however, in 6mm ARC. Because it is the exact same profile, if I did want to use one of the OPS 12 or had one of those over barrel suppressors and a slightly different hand guard, you can actually use one of the OPS 12 suppressors on this barrel.
Getting into the specifics on the barrel, 16-inch, mid-length gas system, 6mm ARC, 1:7 twist, 416R stainless steel barrel that is in this very nice black nitride and is basically a heavy barrel for all intents and purposes. The hand guard on, this build this is the Geissele Mark 13, which has your Picatinny rail sections at the end, because I did want to natively mount a Picatinny bipod to it, I didn't want to have another attachment in the way, so I went with the Mark 13, this is the 13-inch variation.


The upper receiver, this is a BCM standard upper so it is a mil-spec style upper, but the barrel extension on it is a little bit undersized, so you do need to thermally fit the barrel to the upper receiver by heating up the upper receiver to get the barrel to slide in, in theory giving you a little bit tighter fit, hopefully more consistent accuracy, so on and so forth. Unfortunately, the accuracy that we got out of this barrel, at least with a couple factory loads that I tested, was not exceptional, especially when we get into the price to performance, which 6mm ARC is a very expensive round.
The carrier, the carrier is an old Nickel Boron carrier that I had laying around and the bolt is a standard 6.5 Grendel bolt. The muzzle device on the build, this is the Rearden SPB or their single port brake, it is a pretty effective muzzle brake, it's very loud, very blasty, but it's also a very, very size and weight efficient, it's about as long as an A2 and weighs about the same, but does reduce recoil by 40-50%. It also doubles as a mount for the suppressor. The suppressor in question here, this is the YHM Resonator K, which is a 30-caliber can, which you can use with 6mm. 6mm will work on some 556 cans, for instance the Polonium 556 cans, theirs are actually cut for 6mm, so you can use 6mm in their 556 cans. However, that is not the case for all 556 cans, so be very careful and check with the manufacturer before you do something like that.

Most of the time it was suppressed and when running a suppressed we did run into a couple issues, specifically with feeding and extraction, so with this barrel it is set up very well from the factory for unsuppressed shooting, meaning that it will eject high quality ammunition, the ammunition that we were using was the Hornady Black 105 the Precision Hunter 103. It would eject both of those at about 330-ish, which is basically perfect for an AR-15, it would eject those at about 330 with just carbine buffers and carbine springs, however, when we added the Resonator K to the mix we would get drastically increased bolt velocities, it is not a flow through can or a reduced blowbot can, so with those carbine springs and buffers it was way too fast and so we would have issues every couple magazines with ejection, and then also with feeding the last couple rounds because that bolt velocity was just so high that it started to outrun my magazines.


The magazines that I were using when I was unsuppressed, they were 100% reliable, but with the suppressor installed and with the drastically increased bolt velocity I would have issues feeding the last couple rounds, so the magazines that I were using was the ASC 17-round 7.62x39 magazine, 100% reliable when unsuppressed, and E-Lander, I think this is a 15-round also 7.60x39, and the Unimag. Under normal conditions, unsuppressed, it performed very, very well, 100% reliable, no issues feeding, extracting, ejecting, anything like that, with a suppressor it was a little bit finicky. So, if you want maximum reliability out of your 6 ARC gas gun and you're going to be switching between suppressed and unsuppressed you're probably going to want adjustable gas block, adjustable bolt carrier group, adjustable gas key, something like that or at least swapping out your buffers and springs every time you go from suppress to unsuppressed.

That is definitely something I could have done, throwing a heavier spring and buffer combo to slow down that bolt and hopefully improve reliability with feeding and ejecting. On most 556 guns you can run it unsuppressed, throw on a suppressor, yeah, you're going to get a little bit more aggressive bolt velocity, a little bit more aggressive ejection pattern, but it's still going to run just fine. 6mm ARC is a little bit more powerful, has a little bit more energy and, as far as I can tell, tends to be a little bit more finicky, especially with less reliable magazines in general, whereas PMAGs and most AR-15 magazines are 556 mags at this point are basically dumb reliable.


When it comes to accuracy that I was able to get out of this setup it was, unfortunately, a little bit of a mixed bag. We had a target setup at 100 yards, I started out with 105 grain Hornady Black, which was an ammunition that I was actually ableto get a couple hundred rounds at a pretty good price that ended up being about 27 a box, which is expensive but not for 6 Arc, which we'll get into a little bit later on. Anyways, that ammunition shot the first five round group at about one and a half inches at 100 yards, not terrible but not fantastic either, so I did a second five round group with that ammo, just to check consistency, so on and so forth, the second group opened up to about two anda half to three inches, which is borderline unacceptable for a supposedly match-ish ammo with a heavy barrel, 416R stainless steel barrel that's on the premium side of things, it's a couple hundred-dollar retail barrel, and then the last ammunition choice that I had on hand, I only had two ammunition choices, was the 103 Precision Hunter.

The Precision Hunter has a little bit lower of a BC, it's designed more for terminal effects than just true Long Range performance, and that came in somewhere between 1.5 and 2 MOA. A lot of 6 ARC guys who got into 6 ARC are probably also into reloading as it is a very new caliber hat's also very expensive to shoot factory ammunition, average box price for factory ammunition in my area is anywhere between 35 and 50$ a box, it is very expensive and usuallyat best you'll get two types of ammunitions, though usually it's going to be a singular type of ammunition available.

The one factory type of ammo that I haven't tested yet is the ELD-Ms, and supposedly those do perform marginally better and I would hope so, because this should in theory be a very accurate system, we have a very high quality barrel, upper receiver combo that should work well, and we're shooting very expensive ammo, hopefully that would give us very good accuracy on paper, but, unfortunately, as of right now that hasn't happened.
That being said, I have taken this setup all the way out to 600 yards and it was incredibly easy to do so, even with that 1.5 MOA you have a very, very consistent drop, and almost no wind drift. Here in South Dakota it ranges from incredibly windy to no wind at all, so depending on the day that you go out you might have a little bit of mixed results, however, when I took it out to 600 yards I had absolutely no issues with it, it was incredibly consistent at 600 yards as well, and on the same day I took the 6 ARC out, I was also shooting 6.5 Creedmoor out to 600 yards, and while 6.5 Creedmoor definitely has more energy on target, it's always going to win in that category, both of them were just as easy at that 600-yard mark.


600 yards really isn't far enough to prove out something like 6 ARC or 6.5 Creed, probably going to be looking to stretch this out to a thousand yards in the few future, hopefully finding an ammo combo or just breaking the barrel alittle bit more towards getting that accuracy in a better spot, even with a very consistent drop and less wind holds at distance getting something closer to 1 MOA on paper would make it a lot easierto get out to those extended ranges.
AS it stands with this build I am a little bit disappointed in the accuracy that I'm getting out of it, it is a little bit more quirky in terms of reliability when suppressed versus unsuppressed, and it is a great caliber on paper to get out to a distance in an AR-15 platform, however, as of right now, unless you have a ton of money or you're into reloading, it's a fantastic cartridge that you probably shouldn't get into. If you're looking for a more cost effective alternative the 6.5 Grendel is close in terms of performance, it is a little bit slower, a little bit heavier, being 6.5 versus 6-millimeter, so there are to be some advantages with 6mm ARC, however, with 6.5 Grendel, barrels and accessories, and ammunition are going to be much more widely available and a little bit cheaper as well, and you can also get bulk training ammunition that's not particularly expensive at all versus 6 ARC where the cheapest ammo you're going to be getting is probably somewhere between 30 and 40 dollars a box, and it might not perform all that well in your specific barrel. For hand loaders out there, fantastic cartridge, you can do whatever you want with it and it's going to be fairly reliable in an AR-15 as long as it's set up properly.