6mm ARC Round, Too Little Too Late?


Hornady 6mm ARC Ammunition, IMG Hornady Inc
Hornady 6mm ARC Ammunition, IMG @Hornady

Ft Collins, CO –-(Ammoland.com)- 6mm ARC (Advanced Rifle Cartridge) Hornady recently introduced its new, stubby 6mm Advanced Rifle Cartridge (ARC).

It’s basically the 6.5 Grendel, necked-down to 6mm (243cal), and will shoot a 105grain 243cal/6mm bullet.

The 6mm ARC is designed to run in existing in M4 rifle platforms.

I don’t know the velocity, but I suspect something under 3k. Barrel-length is an issue. An eighteen-inch barrel, maybe even a twenty-inch barrel, will likely be necessary to achieve reasonable ballistic efficiency.

Here we go again!

The 6.5 Grendel case (and this is a new case) doesn’t leave much meat around the cartridge head on the existing M4 bolt. One issue with the 6.5Grendel (in heavy use in the M4 platform) has been chronic bolt breakage. Maybe there is some new metallurgy, similar to what POF uses on their Revolution Rifle (7.62×51), but otherwise, I see bolt-life issues with this new round.

This new cartridge represents a ballistic performance improvement (improved range and penetration). No doubt. So does the 6.8SPC, which has been around and endlessly tested since 2004.

Despite all our conversations on this subject, I suspect DOD will be continually fielding M4s in 5.56×45 for at least another 10 years.

There are those who are naively seeking a single cartridge that will run in short M4s, but also render adequate performance in “designated marksman” rifles, sniper rifles, GPMGs, and also be available in both supersonic and subsonic versions.

Can we “have it all” in the same cartridge? It isn’t physically possible.

To convert existing M4s to 6.8SPC, or this new round for that matter will require a new bolt carrier group, new barrels, new magazines, maybe new springs and buffers. Even then, there will be inescapable start-up issues that cannot possibly be foreseen. There always are.

And, brass cartridge cases may be replaced with plastic! What could possibly go wrong?

The point is that this tardy update to the M4 rifle, even if it were implemented right now, is already thirty years late.

We desperately need a 300m auto-loading infantry rifle that shoots through-and-through things, and we haven’t had one since 1964. And at the rate we’re going, it will be yet another ten years before we get one.



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Xaun Loc

As an old-timer I appreciate all the advances in interior, exterior, and terminal ballistics that we are seeing, but I really wish that the industry would settle for just one or two new Wonder Rounds each week.

Despite all the hype, by the time we see any honest independent information about this round, someone else will have released yet another magic silver bullet that claims to punch one-hole groups at absurd distances while also being ideal for every other possible use of any rifle.


Life is all about choices. The trick is to make as few bad ones as possible.

Old Vet

Don’t think you are giving the pro’s at Hornady a fair shake here. Let’s see how it performs in the real world and then do another write-up.


Um…if you treat the caliber as the constant, treat the case as the variable…if we compare like weight projectiles from the variable case selection types, then you see that the Grendel in 107gr performs the same if not better than the smaller ARC. And, this has been available for over 10yrs.

Matt in Oklahoma

I doubt it will do what the military wants and I doubt any powder fueled cartridge will do what it wants especially your desired 30s. They want body armor punched at hundreds of yards with little recoil and a small lightweight compact package. It’s time to look beyond powders and into the next phase.


The Grendel with about 120gr, either jacketed Beryllium Copper bullets, or Titanium Nitride tipped Navel Bronze bullets should be able to do that. This would make an interesting experiment.


What?? No “magic bullet” to be found? That can do ALL things?!??


They had one in Dallas in ’63 didn’t they?

Big Daddy

So they had .223 V and I went out and bought a barrel etc etc now 6mm I think I ll just sit tight.


I think it will be fine for MOST shooters but wont stand up to military use in the M-4. The ballistics are on par with the venerable 6BR. Remington needed to step up on the enhanced barrel extension and bolt they had for the 30 Rem fiasco. Maybe someone in the industry can revisit that.

Randy Willy Johnson

Yep…Remington had a golden opportunity when they developed the .30 Remington AR, which does .308 ballistics in an AR-15 sized platform (I have one; love it!)…but, being Big Green, they managed to completely screw it up, which surprises no one I’m sure. They should have tapped DoD on the shoulder and said “hey, guys…look at this!” I think history would’ve been different by now.


Sounds like a job for a magazine fed Garand.


I’m all in with the 6mm ARC. The weapon weight along with ammo is a significant issue for grunts and scouts. As a combat vet with 5.56 experience, the military has needed a “better cartridge “ since the 1970s. The 6mm ARC will need wide spread use to prove its potential as an effective long range round (500 meters). However, most of us have experience with the AR-15/M-16/M-4 platform and the .243 Winchester round. With heavier bullets, it brings a whole, new perspective for troops. A piece of this is better marksmanship training. Otherwise a better long range round accomplishes… Read more »


However, the Grendel can already exceed the posted performance levels by Hornady.


Thus far mine is very accurate at 700+ yards, am going out this weekend to try longer ranges. Our rifle range has 1 mile targets and you can shoot up to 1 1/2 mile.


They definitely need to come out with a new NIMBY cartridge, aka if it isn’t what I own it is a POS.


Not a bad article, but I am a little astounded that an article evaluating a type of ammunition can be or would be written to include the words, “I don’t know the velocity…”. How in the world can small arms ammunition be evaluated in any useful way without the evaluator knowing the velocity?! Just to help out, I did some deep research — I looked it up on Wikipedia, and it mentions 2,750 to 2,800 fps for bullets in the 103 to 108 grain range.

Wild Bill

I was responding to someone’s comment. That comment disappeared before my comment arrived. Then it gets complicated.
I tried several times. the multiple b is just a place holder.
I think that I am going to lunch!


I’d love to see the 6mm ARC be adopted for the military; in the SHTF eventuality, I want to pick up extra ammo on the battlefield not run to a gun shop to get more. Also, here in Virginia, it is illegal to hunt deer with the .223 round, so I can’t use my AR, therefore I use my AK or my.308. Both are very heavy compared to the AR platform.


300 BLK !

Wild Bill


Last edited 1 year ago by Wild Bill
Wild Bill


Last edited 1 year ago by Wild Bill
Wild Bill

Last edited 1 year ago by Wild Bill

Whoa Bill! I got some Pepto Bismol if you need a swig?


I see you are a “the glass is half full” kinda guy. LOL