The Hornady 6mm ARC for the Desert Tech MDRX

It seems all too frequent nowadays for a new cartridge to jump to the front of every blog, magazine, and ad campaign.
Ammunition manufacturers are always looking for the next best thing to sell. I cant blame them, and I’d much prefer they spend all the money on R&D so the rest of us don’t have to.
At the top of the ammunition game is the big red H that we have all come to know quite well. Hornady has brought some extremely popular cartridges to market in the recent past, the PRC family comes to mind, as does the revered 6.5 Creedmoor.

Watch the video to see the 6 ARC MDRX in action

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Hornady brought another impressive project to the shooting public in 2020 with the introduction of the 6mm Advanced Rifle Cartridge. Introduced in June, the 6mm ARC stands to become a popular red-tipped option. Having seen many of these new cartridges come and go, I was cautiously optimistic for several reasons. Let’s take a look at this round and see what makes it special.


Based on the 6.5 Grendel, the 6mm ARC shares basic dimensions with the Grendel but is necked down to .243/6mm. It shoots heavy for caliber bullets in the 90- to 110-grain range from a 1-to-7.5 twist barrel.

Hornady currently offers three loads of ARC — a 103-grain ELD-X in the Precision Hunter line, a 105-boat tail hollow point in the Black ammunition line, and a 108-grain ELD Match in their match ammunition line. Additionally, Hornady also released loading dies and components for reloading the ARC.

Small frame autoloading rifles already have untold options when it comes to caliber, so what makes the ARC different? According to Hornady the ARC produces a similar if not superior ballistic curve than .308 Winchester. It maintains velocity and drop further than the .308 Win. It does this while also being efficient. The ARC uses smaller, lighter cartridges with lighter powder charges while maintaining a higher level of energy on target than its small-frame competitors. This reduction in weight and powder charge also reduces felt recoil, allowing for rapid hit/miss confirmation and quick follow-up shots.


Of course, specs only matter if the ARC can shoot accurately. The very first time I shot the 6mm ARC at an actual range, I put three shots onto an IPSC target at 200-yards. I was impressed with the results and I knew I wanted one of my own. I grabbed my Desert Tech MDRX to use as a 6mm ARC platform as it offers a multi-caliber design that is easily adapted to large or small-frame cartridges. My good friend and talented gunsmith Eric at ES-Tactical got a quality 6mm barrel blank and we set to work.

The Desert Tech MDRX is a multi-caliber platform that allowed me to test
out the 6mm ARC

The 20-inch 7.5 twist barrel came from K&P, and was drilled, chambered, fluted, and threaded. With the appropriate barrel extension and gas block installed, all I needed was a bolt. The ARC uses a slightly larger bolt face than the .223 Rem, which took steady machining but worked perfectly. The ARC runs at similar pressures to its peers, so I used the same gas settings as a .308 Win. In a matter of a few minutes, the 6mm ARC roared to life.

The MDRX had been zeroed for my .223 barrel, but despite that, the point of impact from the 6mm ARC was very close. So close, in fact, I shot out to 200-, 450-, and 550-yards without zeroing the scope. Shooting standard-size IPSC steel targets isn’t an indicator of record-breaking accuracy or anything, but it felt good right out of the gate. Both factory Hornady match ammunition, as well as handloads, performed well, producing groups that averaged around 0.5 to 0.75 MOA.

Using a US Optics TS8X riflescope calibrated for 5.56 NATO, I reached out to 300-yards across a canyon on a rock that was about 10-inches wide. After hitting it over and over, I figured it was worth trying something further, but the only other target-sized rock I could find was at 960-yards. Without a drop chart, I did a little guesstimating on holdover. I was close but shot over it with an 8 MRAD hold, so I dropped to 7 MRAD, made a better wind call, and sent a second shot. This one found my point of aim with nearly perfect precision. I was more than dazzled, as I continued to place shots on targets all over the mountain. The accuracy of the ARC is superb.

Five-shot group of hand-loaded 105 BTHP Hornady bullets 

It’s fairly well known that the Grendel has trouble feeding on occasion and won’t feed from 5.56 NATO magazines. The ARC, unfortunately, shares that family trait. I temporarily tried some P-Mags until I got proper magazines for the ARC. I found that .300 Blackout mags worked better than 5.56 NATO, but only I loaded a few rounds at a time. Ultimately, I used a few different magazines from Dura-Mag to avoid feeding issues and load to capacity.

It’s worth mentioning that recoil on the ARC is, as Hornady suggested, minimal. Seeing your own hits on steel targets is easy at medium range, and even easier at long range.



I’ve been handloading for many years, so loading the 6mm ARC was as simple as switching out some dies. The powder charges were pleasantly light, I used both CFE556 and BLC-2 for the ARC. Both loads performed well and provided good accuracy and consistency over CCI BR4 primers.

buy 6mm ARC ammo

I used Hornady brass, as well as some resized Grendel cases from Starline. I followed the load data Hornady offers on its website — around 28-grains of powder was where I settled. The Hornady 105-grain BTHP was the bulk of my loading fodder. It’s not too expensive and performs well. No doubt that the ARC will have a deadly encounter in a few months with some Wyoming antelope.


I’m usually slow to jump on new trends — it took me some time to even pick up the 6.5 Creedmoor  but this little cartridge definitely piqued my interest. So much so, in fact, I haven’t used any other barrels in my MDRX since I got this one. Its accurate, smooth shooting makes it easy to spot hits and misses. It also pings targets pretty hard even at significant distances. Aside from the mag issue, the only other drawback is brass as it is a little harder to come by than the average case.

This awesome little cartridge is staying close to me and I’ll be taking it hunting this fall for sure. New loads aren’t always better, but in the case of the 6mm ARC, I think Hornady has a hit.

5 thoughts on “The Hornady 6mm ARC for the Desert Tech MDRX

  1. I have been eyeing the 6mm ARC as a potential for my next caliber conversion. If this was available for either the MDR or the XCR-L, I think I would already have one. The question is who will get there first.

    1. Well, I’d assume you’d have to make one yourself as I did. Not many people making them right now because parts are so hard to find. I assume it could be done on an X95, but I sure wouldn’t. Not when the MDRX is such an easy platform to do it on.

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