6mm ARC Review – Hands-On Testing and Comparisons

by Ryan Cleckner

June 3, 2020

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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.

Why?

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, curiosuly), 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-105-gr-bthp-black-ballistics

Distance (yds)Drop (Mils)5 Mph Wind (Mils)Velocity (fps)Energy (ft/lbs)
1000024541404
2000.30.122901223
3001.10.221331060
4002.00.31981915
5003.10.41835785
6004.20.51694669
7005.60.61558566
8007.10.81427475
9008.70.91303396
100010.71.11185327
110012.91.21093279
120015.41.41045255

6mm-arc-108-gr-eld-match-ballistics

Distance (yds)Drop (Mils)5 Mph Wind (Mils)Velocity (fps)Energy (ft/lbs)
1000023951376
2000.30.123201291
3001.10.221731133
4002.00.32032990
5003.00.41896862
6004.10.51764746
7005.30.61636642
8006.70.71512549
9008.30.81394466
100010.00.91280393
110011.91.11174330
120014.21.21092286

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).

Magazines

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.

Availability/Cost

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

Conclusion

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.

Ballistics

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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99 COMMENTS

  1. the 6mm Grendel is going from a wildcat to a commercial cartridge. Too bad Hornady couldn’t call it what it is…

    1. I assume that you think Hornady should have called the 6mm ARC “6mm Grendel” instead? I don’t follow the logic. Isn’t the 6mm ARC different case dimensions (length, shoulder, etc) and therefore NOT a 6mm Grendel?

      1. Its Hornady’s creation. They can call it what they want. Much like AAC called their version of a Whisper the Blackout. Personally, in contrast to the semantics of it. I don’t think its enough of a distinction based on the fact it’s simply a necked-down Grendel case with the shoulder bumped back ever so slightly. So I do think of it as a 6mm Grendel. All that aside is it something I’m interested in? Yes. And I own a Grendel, but this looks fun and interesting. I don’t subscribe to a zero-sum view. I like diversity and welcome the 6mm ARC.

        1. my comment was aimed at the semantics not the cartridge. the AA trademark on the Grendel is the problem and hornady just pushed the shoulder back on the 6mm AR cartridge then added a letter to the name, not very original and when comparing it to the other 6.5 grendel based ar length 6mm cartridges like the 6 turbo, 6 fat rat, 6 grinch, and the 243 lbc, the 6mm ARC sounds a bit lackluster.

          1. “Grendel” is not a trademark issue anymore. 6mm ARC follows the current Hornady marketing lingo and at the very least is a some what informative name for the cartridge. So many wild cat cartridges end up with really stupid sounding names that don’t tell you much. How would “6 metric wide ass'” sound ? Look at all naming blunders Remington has made over the years… Yes I proudly admit to owning and shooting a REM .260 since 1980. It has been a really great hunting cartridge for me everywhere I have shot with it. If only Remington had called it the “6.5 Hunter” or “.264 Deerslayer” it might have been more commercially successful.

      2. I don’t think Hornady could have named it the 6mm Grendel because of likely trademark problems with Alexander Arms. The 6mm ARC is so close to the 6mm Grendel(wildcat) which is commonly referred to as the 6mm AR(Robert Whitley’s wildcat, the 30 degree not the 40 degree version) it just has a slight decrease in diameter at the start of the shoulder of 0.0008 and the shoulder is bumped back 0.0249 and the length trimmed 0.027. That’s close enough that I don’t doubt that this is anything other than Hornady standardizing the wildcat with just enough tweaks to claim they “developed” the round so they could trademark it for themselves. It’s business as usual between lawyers and everyone needing to put their own name on the same cartridge, otherwise Whitley would have called the 6mm AR a 6mm Grendel from the beginning and Hornady would have just made ammo/brass/dies for it.

    2. Wow what a waste take the same barrel length same weight of Gr bullet and betting it the same as the 6.5 Grendel that been here for over 15 years. Wow what a waste of Hornady efforts and time. rather then making a better Grendel Bullets and design to improve it already.

        1. LOL, but the “updated grendel” as you put it is 10 year old data. Many cartridge designs for the AR beat the 6ARC including those by Whitley. So its not every day you can say the DoD has poorer performing M16’s than its citizens it is tasked to protect

          1. This is similar to the 9mm Dillon that came out in the late 80s for IPSC shooting. Someone noted that it was identical to a wildcat and how could Mike Dillon do that. The reply was, “there are a million reasons why he can, and they all have George Washington’s picture on them”

    3. Badlands Precision produces a far superior bullet to the 108 ELDM or the 103 ELDX. It is their 100 gr 6mm Bulldozer. 1.419 “ long, aluminum tipped. G1 BC 0.580 and a super hog killer. Known to have killed 3 hogs with one shot at 150 yds. Yes, 3 hogs. The second hag was fully penetrated with the bullet already expanded! It can penetrate deeply at any impact velocity. Lets see any lead core bullet do that at 3000 fps impact velocity on a shoulder shot hog. The Bulldozer will have more energy at 1000yds than the 108 ELDM has at 850 yds under standard conditions and weighs 8% less allowing a significantly higher MV. Also stable from the 7.5 twist barrel.

  2. Nice. Solid review! I personally can’t wait to get my hands on one of these. Been a Grendel fan for years, but I’ll take lighter and faster with less recoil just about every time.

    1. Was going to add that comparison tonight. Here’s a preview: I am NOT a fan of the 224 Valkyrie. If you’re going to go to a non-standard cartridge for an AR-15 for better long range performance, the jump to 6mm ARC makes a lot of sense. The 224 Valkyrie doesn’t (to me).

      1. I’ve ordered a 6mmARC barrel from Brownells to rebarrel my .244 Valkyrie. Saves some of that investment.

      2. Valkyrie will use up a barrel faster than 6.5G, where is the 6ARC expected to be relative to 6.5G barrel life? Nice article, very informative, thanks

        1. No clue on barrel life. I should probably worry more about such things but the way I look at it, I worry about barrel life as much as I worry about tire life when talking about a vehicle performance upgrade. Barrels need replaced if you shoot them enough.

    2. At 1000yds, the Valkyrie is flatter – only drops 335″ (9.3mrad), has 378ftlbs, and 1374fps… with the 90g match. From 1000 to 1200 the 6mm ARC appears to be slightly better with the match ammo.

      1. Unfortunately, the .224 Valkyrie doesn’t preform well with MOA!
        Which is why I’m rebarrel my .224 Valkyrie to the 6mmARC, utilizing the BCG, and 6.5 Grendel magazines!

        1. Why would a cartridge not perform well with a system of measurement? If I’m understanding you correctly, that’s like saying a Ford pickup doesn’t run well on liters of gasoline.

  3. I’d love to see how this fares from different barrel lengths. No one wants a 24 inch rifle. The 12-18 inch ballistic numbers will be important. Compared to Grendel numbers for the same barrel length, I’m not sure there will be much difference. I do love the Grendel. I’m sure I would love one of these as well, but as they say experts talk logistics and the logistics of the Grendel are a bit more compelling for now. Time will tell. Try Elander magazines.

    1. Agreed. The numbers I share in my tables out to 1200 are all the actual number from this 18″ rifle and that ammo.

      1. ..and those numbers are good.
        But it’s the V0 out of an 18” that’s interesting, not the 24”

      2. Use the same wight Bullet in each. Then you can get back to US all. Wow .5 mm on hunting is a big difference as well. Look already done this take 108 Molly Gr for the Grendel and your 108 6mm Arc you’ll see the same or Grendel a bit better Same FP/s 2750 -2790 for Grendel, So now it down to ft-lbf, betting Grendel wins at 1000. Also have to use the same BC’s if your doing apples to apples comparison. 🙂

        1. This is my favorite part of cartridge comparisons: folks getting upset no matter what I do. 🙂 “use the same bullet weight” is not the same as “use the same BCs.” And others often comment, if I do either of what you suggest, that it’s not fair because I didn’t use the “best” available for each cartridge.

    2. Meh, AA mags ARE E-landers. Maybe with Barrett involved, they can come up with a decent magazine. Their 6.8 mag is first rate, just a bit short for handloaders.

    3. The Hornady engineer said that they designed the cartridge to be used with an 18 inch barrel for their “DOD customer”.

    4. I’m converting an AR15 with an 18″ BA barrel. Do you have any muzzle velocity data for the 18″ barrel?

      Thanks, great article and I’m excited to get it built.

  4. Fad, should have taken advantage of the 6.8 case head with better bolts for the ar platform.

      1. No idea. Just my personal opinion. Seems they could have reached the performance objective with a smaller higher pressure cartridge. With better mags and bolts. Still like the article btw.

      2. Thank you. If you don’t understand the different reasons behind competing choices, you aren’t qualified to put forth an opinion…in my opinion haha.

        1. More “meat” left on the bolt face with 6.8 but…
          The 6.8(case) would not be able to handle the long bullets(ARC/Grendel). 6.8 was designed to take advantage of shorter barrels, not necessarily longer bullets. 6.8 seems to have a heavy recoil impulse next to Grendel as well. Could someone explain that?

    1. A 6.8 in a profile suited to long range is too heavy for an AR15 platform. It will never be possible to get enough powder behind it to make it work.

      1. I was referring the the6.8 SPC case head size not the bore. Should have realized not everyone was going to be “scoopin what I was poopin”.

    2. I’m glad I didn’t get around to building a 224 Valk/24 Nosler “wildcat” and will now just get a 6 ARC. It almost seemed too easy to run 224 Valkyrie brass through a 24 Nosler die and be done with the paucity of 24 Nosler brass. Of course if 24 Nosler AR barrels were just a click & ship away I might have.

  5. I think the 6mm concept is interesting. After all 6mm is gaining ground in bolt action and many are using vs 6.5.. But I’m skeptical of this article. Are the ballistics of the .223, 6 ARC, and 6.5 Grendel really almost identical at 800 yards according to that chart? The 6mm was an 18″ barrel. What was used for the others? A lot more detail is needed.

    1. Ive given you the measured velocities of this cartridge out of an 18″ barrel AR along with the actual elevation adjustments confirmed at range. There will be no one answer for what 223 or 6.5 Grendel will do without knowing barrel length/velocity of a given system and the particular bullet. Now that I’ve give you real-world data on this new round, you can compare it to whatever other rounds, configuration, and data you like. As I mentioned in the article, even if I went through the nuance of a particular rifle and cartridge, someone would complain. So, it’s easier for me to show you what I got for 6mm ARC in a 6mm ARC review and then you can compare it to your particular system.

      1. Very informative! Looking like a very interesting new caliber to choose from. Maybe I missed it in the article, but what muzzle velocity were you able to get for the 108 grain ELD’s? Using the info you posted, in JBM I got an estimated MV of 2,560 FPS with the majority of the numbers overlapping.

  6. I’m not good with my lingo so forgive me but In regards to hunting and use of hunting ammo ,such as the 123gr for the 6.5 grendel, and not using match ammo, will there be much of a benefit of the 6mm ARC over the grendel in that aspect? When it comes to precise long range shooting it definitely seems there is an advantage in that aspect that the 6mm ARC has over the 6.5 grendel

    1. No. Honestly, the 6.5 Grendel would likely be better for a hunting role because of its higher energy.

    2. What are you hunting? How far are your shots? Have to know at least that much before anyone can give an actual meaningful answer to your question.

    3. I live in a rural area and hunt almost every night of the week year round: hogs, coyotes and bobcats. I use a 6.5 Grendel and have for about 8 months now. It works for me with 100gr ELD-M. 1) this mainstream 6mm Grendel (sort of) is interesting and I like the higher BC on the bullets. I had dreamed of a 6mm Grendel but, without mainstream support like this, I chose the 6.5 Grendel. The 6.5G with the 100gr ELD-M is effective on hogs yet shoots flat enough to reach out over 200yds for coyotes. This 6mm ARC should work very well, too. 2) I use E-Lander magazines for the 6.5G exclusively. I’ve had problems with other manufacturers magazines even though sold as being for the 6.5G. 3) to be clear, many of the current 6.5G bolts and barrels are sold as Type II for a 0.136″ bolt face depth. As fewer, if any, are made for the 0.125″ (or so) depth, this may not matter. But the relic of”Type 1″ and “Type 2” kind of confuses the various AR-15 cartidge based on the .220 Russian cartridge. Occasionally, I still see Grendel stuff marked as Type 2.

  7. Great read and info. Really do enjoy Gun University, thank you. Now just patiently waiting on the advanced book.

  8. Sorry, but if you think the difference between 260 Rem and 6.5CM is equivalent to “rounding differences”, then you don’t grasp the important design improvements made to CM to propel its capabilities well above 260 in long-range use.

  9. Mr. Cleckner made an interesting comment in the fourth paragraph of the second section. He stated that he was confused as to whether the cartridges were siblings or parents/cousins due to his “being from Arizona, not Alabama”. I have a choice here. I can either assume that he is disparaging Alabama by insinuating we know something of incest and inbreeding thus not knowing if we are siblings or cousins; or I can assume that he recognizes the superiority of intellect possessed in Alabama over the average Arizonan thus implying we intellectually understand something he as an Arizonan cannot. I am going to assume the later case. Perhaps a few examples are in order. The entire space race from its inception in the 40’s until today has its foundation at Marshall Space Flight Center in Huntsville, Alabama. We put the man on the moon and we developed the space shuttle and integrated every payload it had as far as I can tell. The astronauts are trained here. Every missile system, radar system, and command and control system designed, developed,and fielded by the US Army is from Redstone Arsenal. Most of the awesome helicopters, supported right here and chopper pilots trained here by Alabamans. Judging from the results, we must be pretty good at that. I am sure you have heard of the Patriot System whose Project Office is where? In Alabama! Huntsville is easily in the top three if not number one for most engineers and scientists per capita of any city in the US and perhaps the world. The average IQ here is off the map. The University of Alabama in Huntsville is without peer in atmospherics, optics, and a host of other disciplines. I make these comments somewhat in jest because I would never insult the great state of Arizona. I am simply pointing out that you need to be careful of old stereotypes. Alabama is a very advanced state today contrary to the antiquated archetype that assumes we are backwards. Why, you may not believe it but we actually wear shoes these days! All kidding aside, Alabama has always been a significant portion of the backbone of the 2nd Amendment so please do not insult your fellow gun lovers. If you are going to insult someone, try California, or better yet, just be careful what you write. Heck, I am sure that Mr. Cleckner knows that many of the greatest snipers came from the south. Live long and prosper Mr. Cleckner! I love your work.

    1. I appreciate your humor! I am very familiar with Huntsville – We used to live there (we loved it) and for the last few years I’ve taught Constitutional law courses at UAH. However, just outside of Huntsville is the rest of Alabama.

      1. “However, just outside of Huntsville is the rest of Alabama.”…..LOFL….As a former “damn yankee” pilot for the AL DoT, I wish I could insert a mic drop meme for that one!

  10. Why don’t the mainstream barrel manufacturers offer extended gas systems and tighter twist for these longer heavy bullets? The dwell time is considerably longer with these hybrid cartridges and I believe that extending the gas system would make them cycle and recoil much smoother. 1/8 doesn’t sound even close to being capable of stabilizing a 108 that long. Maybe I’m wrong. You’re the man, what’s your thoughts?

    1. I’m not sure either in twist. Barrett did say that the rifle I tested had a Rifle 1” gas system on it.

    2. I’ve been shooting a 6mmAR for years now in a quality brand name 1-8″ twist 4 groove barrel that I profiled and chambered with a PT&G 6mmAR reamer. Personally I think 108 gr vs. 105 gr. are at the point of diminishing returns. I run 87gr V Max with H4895 @ 2827 fps and Berger 105 gr VLD Targets with RL-15 @ 2680 fps for best accuracy. On MY good day at 100 yds, the V Max will do a 10 round group within a minute and the 105 gr Bergers have gone 5 shot at .308 as my best. All shots suppressed with rifle length gas system. Point of interest would be the reason of the slightly shorter shoulder on the ARC, I need to load the Bergers single shot as they are too long for magazine loading at .030 jump. Maybe shortened to fit the ELD in the magazine? With proprietary powders from Hornady I would relish this cartridge going mainstream, because I love it! The other safe-mates are getting jealous. Another point of interest is that I built a much lighter weight version with a generic quality barrel for my brother and it shoots very well for a walking hunter. IMO the very best everyman cartridge available for the AR15 platform. I use C Product Grendel magazines and couldn’t be more pleased.

  11. Excellent read. Just seems like if they were serious about the commercial success of this round, they would’ve designed a 6ARC magazine from the start. Which is the reason why I couldn’t commit to 6.8SPC (other than the LWRC), 6.5 Grendel, or 7.62×39 in the AR platform. If I have to grab the weapon for SD, I don’t want that ’empty pit’ in the stomach feeling worrying if I’ll get a FTF/FTE on the first shot using mags of questionable reliability.

    1. I can appreciate your concern. Just want to say none of my 6.8 mags have ever given me any sort of trouble.

  12. Great article! Appreciate the comparisons.
    Agree with the issue on magazines… I recently put together a Grendel build and got E-lander magazines based on positive on-line reviews. They turned out to be junk! Lots of friction resulted in difficulty pushing rounds out, weak springs and bad followers resulted in rounds not coming up and “nose diving into the magazine… Ended up switching to CPDs, and no more problems…! Need more reliable/quality options still!!!

      1. I can’t wait to see how it will perform with Barnes 112… I hope they make some bulk plinking ammo also. I’ve had a lower sitting here for awhile. I was planning on building a 6.5 grendel. No I want to build a 6arc

  13. I’ve spent the last 30 minutes searching for subsonic data. How will it perform suppressed; is that something they will address in the future?

  14. 1. Has anyone tried the PRI mags? I know they were widely considered THE magazine for 6.8 SPC, and Barrett used them in the past. What mags were provided by Barrett with the 6mm ARCs to the DOD

    2. Proof Research also has barrels that can be purchased. You don’t have to wait for the Barretts to become available to get one.

    3. Nice to see other Huntsvillians on here.

  15. Ryan — Excellent work! Thanks for providing this detailed report. But please give credit where credit is due. Robert Whitley came up with this cartridge a decade and a half ago. Read all about it on 6mmAR.com. Robert worked with Redding to create the 6mmAR dies, and he worked with Alexander Arms on the 6.5 Grendel mags. He came up with extensive load data. And he builds complete uppers! There is also a 6mmAR Turbo version, and a 40deg improved version. I assume Hornady’s 6mm ARC is very slightly different from Whitley’s 6mmAR , but Whitley should rightly be give credit for the concept, the design, the execution. And if you want to see Robert’s 6mmAR Black Rifle that can shoot at 100-10X, click here: https://www.6mmbr.com/gunweek068.html

    1. Thank you for adding this. I added a note in the article acknowledging Mr. Whitley with a link to the article you shared.

  16. Following up — here are dimensional comparisons:

    6mmAR (~2006) see 6mmAR.com
    COAL: 2.250 Case Length: 1.515 Case Head: .4449 Shoulder: 30deg

    6mm ARC (2020 copy)
    COAL: 2.26 Case Length: 1.49 Case Head: .441 Shoulder: 30deg

    To be honest, I’m kind of surprised Hornady did not even mention the 6mmAR which has been used for a LONG time successfully.

  17. Ryan-

    Please contact me at the shop (brentonusa.com) for a discussion regarding your magazine issues with this round. The DoD project discussed in your article has recently reached out to us as we make reliable magazines for the 6 mm ARC round. We have had zero reliability issues with our 15 round magazines while shooting both suppressed and not. I do not believe magazines will be a deciding factor in the success or failure of this project. We have been on the fringes of this project for months now but were not invited to the ball until just recently. We had no idea the others working on it were having magazine issues. Go figure…

      1. Any updates on this Ryan? The only thing holding me back at this point is magazine reliability, but that is an absolute deal killer. I have had unreliable weapons in the past and did not enjoy a single one of them.

  18. Cool cartridge, but Hornady should have given a shout out to Robert Whitley, like AAC did for JD Jones when they rolled out the 300 Blackout. Bad move Hornady. Bad move.

  19. Either 18″ bbls velocity sucks at around 2400 fps. A 6×45 or similar on a 223 case can do that pretty much. A 108 eld match with polymer tip will never be used in bv the military so check that if the list. 6.5 Grendel shoots almost as flat at REALISTIC combat/engagement ranges and has more energy. True Hornady is a huge ammunition and component manufacturer but I’m seeing No reason at all why the military would choose this round over the 6.5 grendel or other rounds out there mates to the M4 family of rifles.

    1. The velocity data he published started from the 100 yard mark. I don’t believe he included a muzzle velocity for either of the two rounds, but I could be mistaken. Using a ballistic calculator and the info provided, I’m estimating the MV for the 108 grain is close to 2560 FPS. This also means at 1000 yards, it is still traveling at 1,230 FPS and has roughly 370 ft.lb. of energy.

  20. I primarily hunt with bolt actions and Grendel all I use now. I ran math between them and the 108 eld gives 150 yards more range potential than the 123 eld for similar impact velocity. I suspect that’s a key draw over the Grendel. The Grendel to me is the best hunting choice and can step up to class 3 game better. Range work, class 2 game and military work the Arc makes a lot of sense. C-products 7.62×39 magazine cycles all 10 no issues out of my ruger ranch Grendel. I’d be trying that one in the arc right away.

    1. Then shoot the 6.5 107gr Grendels. I hate it when fake comparisons are made. How about you put a 123gr in the ARC and we compare that to the 107gr 65 Grendel….can you guess the results?

      1. Still, my favorite comments are the cranky caliber comparison comments. If I compare same bullet weight, people get mad. If I compare different bullet weights (that are more suited for each caliber) people get mad.

        Here’s a tip for you all: there’s no free lunch with calibers. We’re launching lead and/or copper projectiles with gunpowder ignited by a primer out of a rifle. There’s more or less powder, bigger and lighter bullets, and efficient and crude bullet designs. There’s only so many combinations.

  21. Thanks for the informative article, did you see any photos of rounds shot into ballistic gel or other actual performance vs different mediums? Was there any further info given on performance in a 12” platform?

    1. They received the exact same package we got to test – the Alexander Arms 6.5 Grendel Mags.

  22. Great article. Informative and useful, thank you very much.

    I’m curious about the optic being used. Is that a Nightforce ATACR 4-16×42? Did the Geissele mount have any cant to it?

  23. First, Thank you for your Ranger service! This is a great read as all you have put out have been. I am wondering if a CMMG Mutant Mk47 style lower with constant curve AK pattern magazines and 308 Winchester bolt face would be a step up in a high round count military environment? There are ten and twenty round small capacity AK magazines of different calibers now that allow a better prone position than with a standard thirty round length. I’m sure there were times you used twenty round aluminum GI magazines with your MK12 when you needed to get low as possible. I know a Mutant style lower and upper ruins the thought of just switching standard AR uppers for a simple caliber change. But for a dedicated hard use military carbine, would it have merit? Thank you again and I am waiting for a part two of your great Long Range Shooting Handbook!

  24. Folks, go back and compare the ballistics to the 6.8 SPC using the 110gr V Ma bullet with a 24″ barrel like this data. It is listed in Wikipedia. Not enough difference to get excited about. And the 6.8 will perform better in a shorter barrel I bet.

    1. I guess it depends on your definition of “not enough difference to get excited about.” Up close? No, there’s not much difference. However, for long range, the 6mm ARC is a big enough difference for me.

      I just went and checked the wikipedia article for 110 V-Max 6.8 SPC and I’ll make a few comparisons. Perhaps I’ll update the article in case other people think the same thing.

      Muzzle Velocity for the 6.8 load you referenced: 2,650 fps. This is at least 100 fps slower than the three loads of 6mm ARC in the article in an equal length barrel. It’s a difference, but to your point, maybe not enough? Honestly, on this metric alone, it would NOT be enough of a difference for me. However, I like this round for its use further away than the muzzle. 😉

      At 400 yards, the wikipedia stats show 31.1 inches of drop for the land you reference at 400 yards. The 6mm ARC, however, drop only 2 mils (27 inches). 6mm Arc only drops 86% as much as 6.8 SPC. For me, this is getting more significant. However, if you don’t shoot long range, which is the entire reason I like this cartridge, I could see how this wouldn’t be enough for you out to around these distances. However, the 6,.8 S{C 100 gr bullet will only have 801 ft/lbs of energy at 400 whereas the 6mm ARC will have 990 ft/lbs of energy. That’s significant for me, but not for all.

      At further distances is where the 6mm ARC blows the 6.8 SPC load you referenced away. For example, at 1000 yards, the 6mm ARC needs 10 mils (33.75 Moa) of elevation. The 6.8 SPC load you referenced, on the other hand requires 15 mils (50.63 Moa) of elevation. To me, a jump from 10 Mils to 15 Mils is VERY significant. Also, the 6mm ARC will have 393 ft/lbs of energy at this distance vs only 224 ft/lbs for the 6.8 SPC – that’s almost twice as much energy for the 6mm ARC. And, as you can imagine, the 6.8 SPC is only going to fall further and further behind as the distance increases.

      So, if you are not shooting long range, your point is fair and I agree. However, for long range, which is what this round is for, it smokes the 6.8 SPC.

  25. I’m a bit puzzled by the YouTube videos of people shooting 6mm ARC AR-15s. Many of them do not seem to group well. One in particular comes to mind which showed an unacceptable amount of vertical stringing. It could have been operator error, but the gun didn’t recoil that much. Many others double group, that is there are three in a group and 2 in a group a bit away. Most of them had 7.5 or 7.7 twist barrels and the close up video of the paper targets frequently showed the point of the bullet not being centered on the hole made by the rest of the bullet.

    The 6mm AR, AR Turbo, Fat Rat, Grinch and so on seem to shoot better even though they are not that different.

    It is interesting that the DoD client went with a 6mm bullet rather than the 6.5mm of the existing Grendel. I have to suspect that there were some differences in terminal ballistics in terms of penetration of heavy clothing or body armor worn by opposition forces.

    It could simply be that Alexander Arms squandered the small window of opportunity to have the Grendel adopted by keeping it proprietary at first. DoD doesn’t simply pay the sort of price for ammo that they wanted.

  26. I shoot 6mm FAT RAT with Berger 105 hybrids. I had to remove thr inner flap of the Alexander 6.5 Grendel magazine and the reweld the case to get a reliable feed. Not a problem, but something to consider with long bullets.

  27. Regarding an evaluation of the C-Products Magazines – A few months ago I took delivery of a CMMG Resolute 300 6mm ARC upper with a 16 inch barrel that came with 3 C-Products 10 round magazines. The magazines and the upper have performed flawlessly; I’ve yet to have a failure to feed, a failure to eject or a jam. At that point I ordered two of the 20 round C- Products magazines and they have also worked flawlessly and are easy to load.

    Here is the only issue I’m having with the upper – I have tried all three types of Hornady ammo, the Black, ELD and Precision Hunter. When shooting groups at two or 300 yards, regardless of the ammo I average about 1 1/2 to Two MOA groups.

    As I bought this gun for a coyote hunting, I consider this problematic. If you’re wondering why I got the 16 inch barrel, I was not really looking to keep the weight down but I’m not that tall I will be carrying in the field a suppressor on the front end.

    At this point I’m going to wait and see if Federal or another ammo company comes up with another 6 mm arc ammo that can possibly improve the accuracy of this round. Until then I’ll just put this up on the side because I don’t consider it effective for the type of coyotes hunting I’m looking to do which can include shots out in the 200 to 400 yard range.

    Does anyone else have the same accuracy issues I’ve mentioned?

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