CMMG Endeavor 6MM ARC, Does it Live Up to the Hype? Video Review

U.S.A.-(AmmoLand.com)- The day that Hornady announced the new 6mm ARC cartridge, I begged the poor guy I know at CMMG to send me a rifle. I bet he is so sorry that he ever gave me his number, and I’m sure I’m blocked at this point. The 6mm ARC sounded cool to me and I know that CMMG builds excellent, and extremely accurate rifles so I felt they would make a great combo. CMMG did get the rifle right out to me, which was awesome on their part, but it took me a few weeks to track down some ammo. Never the less, once I got both the gun and the ammo, I finally got to head to the range and see if 6mm ARC lived up to the hype.

CMMG Endeavor in 6mm ARC, Vortex Strike Eagle, and KGMade R30 Suppressor

If you’ve been living under a rock, here’s the basics on the 6mm ARC. The story goes that DOD approached Hornady to see if they could develop a round that would have the long range capabilities and deliver energy on target similar to 308, yet feed out of a standard AR-15 platform. The idea was the constant; I want the power of the 308, but I want to fit it in my AR15. Basically, can I have the power of a bull dozer, but I want it to fit into my sports car. One serious thing to consider, if it can be accomplished, that would give the shooter a 30% weight savings on both the ammo and the platform. A pretty big deal if you have to hump it through the mountains of Afghanistan. Not as big of a deal moving it from my truck to the shooting line, but it is still appreciated.

308 next to 6mm ARC

Basically, Hornady took their 6mm projectile, which has a very high bullet coefficient (that means it’s extremely aerodynamic), and combined that with a 6.5 Grendel case. Giving that 6mm projectile the most powder it possibly can, to get it to speed. Here’s how it shakes out; as far as range, the 6mm ARC should stay supersonic just longer than 308 out of the same length barrel. Once a projectile passes from supersonic to subsonic, accuracy and energy fall off. While you can hit a target past that point, it’s not practical for any real-world application. Meaning, that with the same length barrel, you’ll get longer or at least the same range with 6mm ARC compared to 308. When you look at energy, the 308 is far more powerful at shorter ranges. However, as you get to longer ranges they get closer to the same energy, but 308 always does edge out the 6MM ARC. That means, let’s say if your expected target is at 500 yards or better, both rounds will have similar energy on target, with a slight edge to the 308. However, it’s close, and you get that massive weight savings with the 6mm ARC. 

Shooting the CMMG Endeavor in 6mm ARC, Vortex Strike Eagle, and KGMade R30 Suppressor

This is my first time playing with an actual Endeavor, which is CMMG’s lineup of long-range, precision built ARs. I received the 300 series which has all the bells and whistles; as always, I was extremely impressed with how CMMG has equipped this rifle. You’ll of course get all the goodies you would expect from CMMG; 7075-T6 aluminum receiver sets, their full-length MLOK handguard, and of course their awesome ambidextrous charging handle. What really impressed me is some of the absolutely top-notch accessories CMMG puts into the rifle. The 300 series Endeavor comes with a Geissele SSA two-stage trigger. This trigger is phenomenal, and I love a really nice two-stage trigger for long-range precision shooting. Another feature that I love on the 300 series of Endeavor is the Magpul PRS stock. There are a lot of options available currently for a precision stock on your AR-based rifle, and most of them are cheaper than the Magpul PRS. However, I have yet to see one better than the PRS and I’m so glad that CMMG didn’t skimp on this component. The Magpul PRS gives you a rock-solid foundation, and when combined with the Geissele trigger and the very well built CMMG endeavor, it gives you a phenomenal platform no matter what caliber you are using. 

Basically, there are a few rounds that are all chasing that title of the most powerful, longest range, that can be shot out of a standard AR15. For those that don’t know, the major contenders are 6mm ARC, 224 Valkyrie, and 6.5 Grendel. There are a few more, but I feel these are the top options. I want to be upfront, that I own a 224 Valkyrie, have a lot of experience with 224, and I will say my experience has been more positive than most. I do not have a 6.5 Grendel. While I have shot it, my experience with 6.5 Grendel is somewhat limited. So most of my comparisons will be to 224 Valkyrie. Where 224 Valkyrie falls short for me, is I lose some consistency at 1000 yards. To me that means the bullet is running out of gas and becoming unstable. Out to about 700-800 yards my 224 is razor accurate and extremely consistent, but that jump to 1000 hurts it a little.

22 Nosler, 224 Valkyrie, and 6mm ARC

6mm ARC was a noticeable improvement; not only was it very consistent at 1000 yards, but it hit the 1000 yards plate with authority, like it still has quite a bit of power left. It would be interesting to get 6mm ARC on an even longer range and see how far you could stretch it. 6MM ARC out of the CMMG Endeavor was also very accurate, easily sub MOA at 100, and even some of the groups that we got at longer ranges were very impressive. At 1000 yards, we consistently put up groups that were less than 10 inches, with an average of about 7 inches. That is the kind of consistency that I was hoping for, and all sub MOA at 1000 yards.

CMMG Endeavor in 6mm ARC, Vortex Strike Eagle, and KGMade R30 Suppressor

I’d like to spend some more time shooting the 6mm ARC, but my initial impressions are that it would seem to live up to the hype. For me, it was much more consistent at 1000 rounds than my 224 Valkyrie, which is what I was hoping it would be. All the while keeping it in the very compact AR15 package. I had to send this CMMG Endeavor back to CMMG so that they could get it in the hands of another reviewer, and it was a sad day when I had to let that Endeavor go. However, when CMMG gets some more in stock, I will be getting my own Endeavor in 6mm ARC, because I do feel there is some validity to this round. Now, if you’re happy with the performance of your 224 Valkyrie, or your 6.5 Grendel, I’m not sure that you need to hop on the 6mm ARC bandwagon. However, if you feel that either of those rounds hasn’t quite lived up to your expectations, and are looking for a little more performance at a slightly longer range from an AR-15 sized rifle, I do feel that 6mm ARC is probably the best offering.


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