6mm ARC Review – Hands-On Testing and Comparisons

by Ryan Cleckner

June 3, 2020



Hornady just released their newest cartridge, the 6mm ARC or “Advanced Rifle Cartridge”, and Gun University was invited out to the range to test it and get a sneak peek of its capabilities before its launch.

If you know me, you know I’m usually suspicious of new cartridges. So, how did the 6mm ARC perform for us at the range and what do we think about this new 6mm cartridge? Read the rest of our 6mm ARC Review to find out…

6MM ARC Ammunition

Available at Brownells.com

Check Price

6mm Advanced Rifle Cartridge Background

6mm ARC Specs

  • Bullet Diameter 6mm / .243
  • Bullet Weights 103-108gr
  • Muzzle Velocity ~2,750 fps
  • Muzzle Energy ~1,800 ft/lbs
  • Cartridge Length 2.26″
  • Case Length 1.49″
  • Head Diameter 0.441″
  • Shoulder Angle 30 Degrees
  • Max Pressure 52,000 psi

The 6mm Advanced Rifle Cartridge (6 ARC) by Hornady is a new cartridge that can fire a sleek 6mm (.243) caliber projectile around 2,700 fps with minimal recoil and the 6mm ARC is short enough to fit within the dimensions of a standard AR-15 magazine and it performs very well out of an AR-15 with an 18 inch barrel (what we tested).

The parent case for the 6 ARC is the 220 Russian. Well, kind of.

The base of the cartridge is the same diameter and the overall length of the case is similar, however, the 6mm ARC does not share the generous case taper of the 220 Russian. You couldn’t just push a 220 Russian through a reloading die to get a 6mm ARC.

Technically, the 6mm ARC is more closely related to the 6.5 Grendel or 6mm PPC. But, since they each share the 220 Russian as their parent, maybe they’re siblings? Or parent/cousins? Crap, now I’m confused – I’m from Arizona, not Alabama.

The easiest way to explain the origin of the 6 ARC, or what the 6mm ARC is, is to call it a modernized version of the 6.5 Grendel but with a 6mm bullet.

Those of you that know the nuances of wildcat cartridges (cartridges that are not regularly commercially available and instead mostly common with hand-loaders who tailor their own rounds) already know that 6mm versions of 6.5 Grendel-like cartridges already exist.

Some examples include 6mm AR, 6mm PPC, and more. In fact, this new cartridge’s dimensions are similar to the 6mm AR by Robert Whitley.

So, why did Hornady come out with the 6mm ARC in the face of numerous other options? Easy. They are a manufacturer that is willing to standardize a particular performance concept and take a cartridge to market and make it “mainstream” with SAAMI specs. There’s a lot to be said for for standardizing some available wildcat options and then providing factory options.

After all, they did this with the 6.5 Creedmoor – the .260 Remington already existed for many years (as did some other similar options). However, Hornady wasn’t claiming to invent anything particularly novel. Instead, they took the torch, standardized (and modernized) the dimensions, and brought it to market with accessories and load data that allowed it to be easily adopted by the industry.

It appears that is what they are doing here by making an AR-15 compatible cartridge that is easiest explained as a 6mm version of the 6.5 Grendel with some modern case design.

Why did they want to do this?

Rec 7 6mm ARC package

Well, a certain Department of Defense (DOD) customer, who has already received their Barrett Rec-7 Rifles chambered in 6mm ARC (which is the configuration we got to play with), wanted increased energy and long range performance over 5.56mm NATO without
needing to jump up to a larger platform like the AR-10 and they wanted light enough recoil that their rifles could still be easily used in AR-style engagements with rapid shots.

The final product for the DoD customer that we tested was a cooperation from a few industry members: Barrett, Hornady, Nightforce, Geissele, OSS Suppressors, and Proof Research. For more info on this government-used 6mm ARC platform, check out our article on the project: COMING SOON

Here’s what Hornady is sharing about the performance of the 6 ARC cartridge. You can see the comparison to 308 Win / 7.62 NATO not because Hornady is trying to claim that 6mm ARC is meant to replace it but rather meeting “hybrid” performance in the smaller package was the objective of the government contract. Also, there’s a “not available to the public bullet” that performed as well on real targets and barricades at distance as the 308 Win (not the same “energy” but similar or same penetration, effect on target, etc.)

6 ARC (Advanced Rifle Cartridge) Features

1 Efficient, high B.C. 6mm bullets

Bullets available in factory loads from Hornady in both tipped and BTHP.

2 AR-15 Magazine-Length Cartridge

Overall length fits AR-15 magazine dimensions.

3 Modern Case Design

Features common to modern case design like 30 degree shoulder.

4 Shares 6.5 Grendel Base Diameter

Works with AR bolts currently available in marketplace.

6mm ARC Review – OUR TAKE

“Ok, here we go. [Sigh]”

That’s what I thought as I was walking in to meet with engineers about this new round from Hornady and there’s a good chance that’s what you’re thinking as you read this now.


Well, in my case it’s because I’m suspicious of new cartridges because often they really don’t do anything better than something else that’s been around for many years and they’re usually introduced as “ground-breaking innovation” and the “ultimate cartridge” and a good number of them are left in the dust while consumers have firearms in that chambering that are gathering dust.

Now, just because a new cartridge isn’t earth-shattering in its performance compared to other cartridges doesn’t mean that it isn’t a serious contender. There’s a LOT to be said for more efficient case designs, bullets, and standardizing myriad wildcats.

The easiest example for me here is the 6.5 Creedmoor – an incredibly popular cartridge and the clear winner in terms of adoption of other similar calibers. If I had jumped when Remington released the 260 Remington in 1997, I’d be stuck with rifles for which I can find ammo, but not NEAR as widespread as I can find 6.5 Creedmoor. (If you didn’t know, these two cartridges are effectively rounding errors of each other)

So, just because a new cartridge isn’t vastly different from other offerings doesn’t mean that it won’t take off and be a popular cartridge. Likewise, the first cartridge to offer something unique can sometimes fade away when a better marketed/standardized approach later arrives. e.g. 300 whisper -> 300 blackout

So, with some optimistic caution I walked in to our meeting about the new 6mm ARC much like I expect you’re reading on…

After learning about the joint project between Hornady, Barrett Firearms, Proof Research, Geissele, Nightforce, and OSS Suppressors to provide Barrett Rec-7s chambered in 6mm ARC to a Department of Defense customer, we started talking about the details of the 6mm ARC cartridge.

Within a couple of minutes, I asked “So, effectively a modernized 6.5 Grendel?” Yes, I oversimplified it. But, I even got an engineer to agree with me. 

It even uses the same bolt and we used Alexander Arms 6.5 Grendel-marked magazines in our testing. Here you can see the larger 6mm ARC bolt-face on the right compared to a standard 223 bolt on the left.

We were very lucky to have a chance to shoot the Barrett Rec-7 with an 18″ Proof research Carbon Fiber barrel on two separate days/trips to the range. This gave me a chance for initial impressions, a few days to think about it, and then a chance to confirm my thoughts on another trip.

No testing of this system produced accuracy worse than 1 Minute of Angle (MOA) out to 1250 yards (that is, of course, if you ignore figuring out the wind…. I’m referring to being on target and shooting an actual group at each distance).

Most of the shooting was conducted standing off of a tripod from 300-615 yards on steel targets. We decided to put a GoPro camera at the 600 yard gong rack and I, not wanting to hit my camera, chickened out and got into the prone to shoot off of a bag:

My first trip to the range started with some skepticism. Sure, I believed that the Hornady engineers would make a great cartridge and I was sure it would do everything I was being told. However, I wasn’t sure it’d be good enough to justify switching to a new cartridge (something that I’m loathe to do for my personal supply-chain concerns).

My second trip, however, started with some excitement over getting to shoot the round again. This was important for me to note. Sure, I love shooting but at this point if I’m actually getting “excited” about something, it must be special.

What we loved about the 6mm ARC:

In the Barrett Rec-7 is was super accurate and fun to shoot!

On almost every shot I made (except for when I was in the prone, curiously), I was able to spot my own impacts. The energy was enough to make the impact noticeable while the recoil was low enough to allow me to stay on target without much effort (even on the tripod).

If you’re looking to get something with better long range ballistics out of your AR-15, this new 6 ARC allows a performance upgrade without a platform upgrade. This rifle was way more portable than a larger AR-10.

By the end of my testing over a couple trips, I am now a fan of the 6 ARC and will be getting my own. For banging steel out to 1,200, it is all I need and it is more enjoyable to shoot out of a semi-auto gas-gun than even the already comparatively mild 6.5 Creedmoor. The platform is small and lite enough, it isn’t relegated to dedicated long range duty – it could easily be used in an assaulter role.

This makes two fairly recent releases from Hornady that convinced me to jump on early. This 6 ARC and the 300 PRC.  To prove I’m not a fanboy of new Hornady cartridges, I’m not a fan of the 6.5 PRC – there’s nothing “wrong” with it, I just don’t get it. 

What we didn’t love about the 6 ARC:

The magazines leave a lot to be desired.

In order to use the 6 ARC in an AR-15, we needed to use 6.5 Grendel magazines from Alexander Arms. In comparison to the other gear, the magazines seemed cheap.

Also, they didn’t work great. (that’s kind of important)

Part of the reason may be their design/quality, however, another reason is that the new shoulder location on the 6 ARC from the 6.5 Grendel makes the Grendel mag less than a perfect fit.

This is the only thing that gives me apprehension about this round – without multiple quality sources for magazines, the cartridge might never get a chance. Come on Magpul, give us a 6 ARC mag.

Hornady 6mm ARC Ballistics

The 6mm ARC clearly has improved ballistic performance over .223/5.56. It is a relatively fast and heavier bullet with a modern high ballistic coefficient bullet.

This translates into ballistic performance out of an AR_15 platform that drops less due to gravity, drifts less for wind, and hits harder on the target.

Here are the load details for each of the three factory offering from the developer of the cartridge, Hornady. They’ll first be coming out with a cartridge in their “match” line with a 108 grain ELD-Match bullet for excellent long range performance and another loading with a 105 grain boat-tailed hollow point bullet in their “black” line.

They’re planning on bringing out the third product line, a hunting cartridge with their 103 grain ELD-X bullet by Fall of 2020. Let’s hope that it’s in time for hunting season.

Spec108gr ELD Match105gr BTHP Black103gr ELD-X
Bullet TypeELD MatchBTHPELD-X
Bullet Weight108gr105gr103gr
Muzzle Velocity (24" barrel)2750 fps2750 fps2800 fps
Muzzle Energy1813 ft/lbs1763 ft/lbs1793 ft/lbs
BC (G1)0.5360.5300.512
BC (G7)0.2700.258
Sectional Density0.2610.2540.249
Min. Twist Rate1:8"1:8"1:8"

Ok, just looking at the load data/basic ballistics for the 6mm ARC is better than nothing, but I know what you’re really wonder….”how does the 6mm ARC compare to other cartridges?”

I’ll attempt to answer that here. If past experience is any indication, we’ll see plenty of comments of upset folks no matter what we do. For example, if we use the flattest shooting load of a particular cartridge for comparison, we expect complaints that we didn’t choose the “standard” configuration or the load with more energy.

So, here’s what we’re going to try to do: make an apples to apples comparison when possible. Because Hornady is the only manufacturer of this round so far, we’ll try to compare the 6mm ARC to other cartridges from Hornady in similar product lines.

Our test rifle, a Barrett Rec-7 with an 18″ carbon-fiber Proof Research barrel, was shot out to 1,250 yards for testing. Here is the actual data gathered from the firearm and available ammo (not just theoretical) via chronograph as well as confirmed groups on targets.

Both the Hornady 105 gr BTHP and 108 gr ELD-Match data is included:

6mm ARC 105gr BTHP Black Ballistics

Distance (yds)Drop (Mils)5 Mph Wind (Mils)Velocity (fps)Energy (ft/lbs)

6mm ARC 108gr ELD-Match Ballistics

Distance (yds)Drop (Mils)5 Mph Wind (Mils)Velocity (fps)Energy (ft/lbs)

6 mm ARC Comparisons

And now, let’s compare the new 6 mm ARC to some other calibers.

First, it seems most obvious to us to compare the 6 mm ARC to the most common cartridge in an AR-15 platform, .223 Remington and the most obvious commercially available relative, the 6.5 Grendel.

Here is a graph produced by the Ballistic AE app showing the trajectory and energy comparisons of the Hornady 105 gr BTHP Black 6mm ARC to the factory available offerings of Hornady 75 gr BTHP Black .223 Rem. and Hornady 123 gr A-Max 6.5 Grendel (no BTHP by Hornady is available for comparison).

The red line is 6mm ARC, the blue line is .223 Rem, and the green line is 6.5 Grendel.

6mm ARC vs 223 Rem

Hornady’s new 6mm ARC handily beats the 223 Rem/5.56 NATO in all but two areas: magazine capacity and availability.

External Ballistics

As you can see from the graph above, the 6mm ARC drops less than 223 Rem/5.56 NATO and it has more energy, too. As it flies through the air, the 6mm bullets also drift less due to wind.

Yes, heavier match-grade 223 Rem can be shot out to 1200 yards semi-accurately. However, the 6mm ARC is much more effective for the job in my experience.

Terminal Ballistics

The 6mm ARC by Hornady clearly hits harder.

The higher energy isn’t just noticeable on the graph above, we could hear a distinctly louder sound/heavier impacts on steel targets.

Of course, this comes at some recoil cost, but not much at all. The 6mm ARC is a pussy-cat compared to other cartridges (especially if you consider jumping up to an AR-10 for 308 Win or 6.5 Creedmoor).


As you saw above in our review, the achilles heel for the 6 ARC is the magazine. First, a special magazine is needed. Second, that special magazine still isn’t quite “right.” Third, the capacity is lower for 6 ARC as compared to 223 Rem in the same outside-dimensions for a magazine.


Clearly, 223 Rem is WAY more available and less expensive. Also, there are many more 223 specific parts for AR-15s.


If you’re looking for plenty of inexpensive ammo and you’re interested in the lowest recoil and highest capacity, then stick with 223 Rem / 5.56 NATO for your AR-15.

However, if you’d like to keep the same rifle platform while gaining an increase in energy and long range performance without much more recoil, then the 6mm ARC is for you.

Note how the recoil is light enough with 6 mm ARC that I can use the Barret Rec-7 like a typical AR-15 for two rapid shots (controlled pair/double tap). This would not be as easy with an AR-10 in a larger caliber:

6mm ARC vs 6.5 Grendel

It’s pretty fair to simplify the 6mm ARC cartridge as “effectively a 6mm version of 6.5 Grendel.”

The 6mm ARC, however, is not simply a “necked-down” 6.5 Grendel because the shoulder is also back a bit on the 6mm ARC.


As you can see from the graph above, the 6mm ARC has better trajectory but the 6.5 Grendel has better energy – but not much. In fact, the jump in energy from 223/5.56 to 6mm ARC is more than the jump again to 6.5 Grendel.

It’s tough to pick a “winner” here without knowing your situation. If you already have a 6.5 Grendel or you want the most energy, then it’s probably 6.5 Grendel for you. However, if you’re looking at both to consider and you like the idea of low recoil and long range performance with more efficient bullets, you should get a 6mm ARC.

Here’s my situation: I like long range shooting and I don’t have a 6.5 Grendel already so I’m going to be getting myself a 6mm ARC. Maybe Barrett won’t want their Rec-7 back?

6mm ARC Ammunition Pros and Cons

  • More performance and energy than 223/5.56
  • Uses modern high B.C. 6mm bullets
  • Low enough recoil to “spot” own rounds
  • Standardizes popular wildcat cartridges in factory offering
  • Good all-around cartridge: target shooting (especially long range), hunting (on the lighter end), defense/tactical
  • Makes use of extremely common AR-15 platform and already available bolts
  • Requires special magazine to function well (and still not perfect)
  • More expensive than 223/5.56
  • Less than 30-round capacity
  • Brand new – longevity unknown

6MM ARC Ammunition

Available at Brownells.com

Rifles Barrels in 6mm ARC

If you’ve already got an AR-15, you can convert it to a 6 ARC by replacing the barrel, changing the bolt, and using a dedicated magazine.

Here are some barrels chambered in 6mm Advanced Rifle Cartridge:

1. Faxon 6mm Arc Barrel

Faxon Firearms makes quality barrels, and other parts, for many types of firearms. We’ve used a few Faxon barrel in our own guns and have been very happy with them (plus they’re good guys, too). These 6.5mm ARC barrels are available in four lengths from 14.5″ to 20″  

2. Ballistic Advantage 6mm ARC Barrel

Ballistic Advantage has a strong reputation for making quality AR-15 parts… We have no hesitation in using one of their barrels, however, we have no direct experience with them. 

3. Aero Precision Upper

If you’re not comfortable installing your own AR-15 barrel, or you’d rather have the ability to switch easily between calibers, ordering an entire upper receiver in 6mm ARC is the fastest and easiest option. Snap it on, feed it 6 ARC ammo, and enjoy. 

AR-15 Bolts in 6mm ARC

Once you’ve got a barrel chambered in 6mm ARC, a bolt is all you need to complete your conversion of your AR from its current caliber to 6 ARC. To be clear, a “6mm ARC” specific bolt is NOT required… a 6.5 Grendel bolt will work as well.

Here are some bolts that will work with the 6mm Advanced Rifle Cartridge:

1. Brownells Bolt Carrier Group

Brownells makes a quality bolt carrier group (not just the bolt…the entire assembly) at a good value. We’ve used Brownell’s bolts before without issue and we wouldn’t hesitate to do so again. We really like the Nitride coating on these bolts.  

2. Faxon 6mm Arc Bolt Carrier Group

Faxon’s complete bolt carrier groups are a great value. These are not their higher-end line but they are great for weekend-hobbyist AR-15 builders looking for parts that will be reliable. 

6mm ARC Magazines

As we mention above, we’re not convinced that the magazines are figured out yet. We had less than desirable results with the Alexander Arms 6.5 Grendel mags. They worked, but there could be improvements because the 6mm ARC is slightly different than the 6.5 Grendel.

Here are magazines for the 6mm Advanced Rifle Cartridge:

1. E-Lander 6.5 Grendel Mag

We have no experience with this magazine but it has been recommended to us as a better solution for an AR-15 in 6mm ARC.  

2. C-Products 6.5 Grendel Magazine

C-Products is a big name in both aftermarket and OEM magazines. Like the E-Lander above, we have no direct experience with this magazine. If you try it and like it, let us know. 


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About Ryan Cleckner

Ryan is a former special operations sniper (1/75 Ranger) and current firearms attorney, firearms industry executive, university lecturer, and bestselling author of the Long Range Shooting Handbook.

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