6mm ARC Cartridge — SAAMI Specs, Build Requirements, Videos
In June 2020, Hornady introduced the 6mm ARC, a new SAAMI cartridge optimized for AR-platform rifles*. The new 6mm ARC is basically a 6.5 Grendel necked down to 6mm, with the shoulder moved back around .030″. That pushed-back shoulder does reduce case capacity (and velocity), but we assume Hornady did that to create a shorter, proprietary chamber so people could not simply neck-down Lapua 6.5 Grendel brass, as has been done for years with Robert Whitley’s outstanding 6mm AR wildcat.
CLICK Image for official SAAMI Specifications:
If you are intrigued by the 6mm ARC, you’ll find the products you need at Brownells — uppers, barrels, bolts, and magazines. Brownells also sells Hornady-made 6mm ARC factory-loaded ammo, but most varieties are out-of-stock right now, as is the 6mm ARC brass. More brass and ammo should arrive soon. Midsouth is also taking brass/ammo backorders. For general information, see 6mm ARC Info Page.
What Is the 6mm ARC Cartridge?
The 6mm ARC cartridge is a new SAAMI-spec cartridge based on the 6.5 Grendel case necked down for 6mm bullets, with the shoulder moved back 0.030. Yes it is designed to run in AR15-platform rifles. You’ll need a new barrel, bolt, and mags. If you already have an AR chambered in 6.5 Grendel, the ONLY thing you need to change is the barrel. Everything else — bolt, magazines, gas system – is compatible with 6mm ARC.
▶ Official SAAMI Cartridge (not wildcat)
▶ Fits standard AR15-platform rifles
▶ Fits Short/Mini action bolt rifles
▶ Efficient short, fat case design
▶ 30-degree case shoulder
For more INFO, see 6mm ARC Info Page.
What Do I Need To Shoot the 6mm ARC?
Faxon and Ballistic Advantage are already producing barrels, with more manufacturers sure to follow. All the other required components are already on the market for 6.5 Grendel rifles. Aero Precision already offers complete 6mm ARC uppers.
If you’re converting a standard 5.56×45 mm (.223 Rem) AR15 upper to shoot 6mm ARC, you’ll need a 6mm barrel, a Type II 6.5 Grendel bolt carrier group, and new magazines. Some folks have suggested standard AR mags will work, but trust us, you want the magazines that have been designed for 6.5 Grendel. All the hardware you need is currently available at Brownells. And Brownells also sells complete Aero Precision 6mm ARC Uppers, starting at $749.99.
6mm ARC Videos from Hornady (18 Total)
* While 6-6.5 Grendel shooters are known to run stout pressures, the new 6mm ARC cartridge has a relatively moderate Maximum Average Pressure (MAP) rating of 52,000 psi according to the official SAAMI specifications. For a variety of reasons, is wise to keep pressures in a semi-auto rifle moderate. Don’t chase the velocities you might get in a bolt-action gun.
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Tags: 6.5 Grendel, 6mm ARC, 6mm Creedmoor, 6mmAR, Brownells 6mm ARC, Hornady
6mm PPC?
I really hope this takes off. I love the concept and would likely re-chamber my 6mmBR into this for ammo availability.
I wonder if this will make inroads in benchrest, when better brass is vailable?
It is going to be interesting to see bolt life. The only powders that is available commercially that will get 105-108gr bullets to 2750fps under 52ksi pressure are temperature sensitive ball powders.
I like the cartridge but the dam name sucks. Why call a cartridge an Arc defined as part of a circle ⭕️. They should’ve just left it at A.R.C. Advanced Rifle Cartridge. Arc is just plain silly
I ordered a 24” barrel from Brownells. I plan on doing a build when parts come available.
Personally, I think this is the perfect choice for an AR Velocities for long, high BC bullets are perfect for long barrel life and excellent accuracy.
Already adopted by one Army Spec. Warfare unit, this cartridge has lots of potential as a commercial offering as well.
With the current political situation, it’s most likely going to take me a long time to get all the parts together.
I ran the Hornady 108gr ELD through the Berger bullet stability calculator after looking at targets fired by various people with 7.5 and 7.7 twist barrels. The groups showed signs, at least to me, of not being adequately stabilized which is why I went to the calculator. According to the calculator a 1:7 twist barrel is necessary to adequately stabilize that bullet.
That makes me wonder why Hornady chose a barrel with too slow a twist after all the development work they did.
Purchased a 6mm Arc upper from Sanders Armory. It took 4 months to come in. Brass is still back ordered. Made brass from 6.5 Grendel Cartridges. After finding the correct C.O.L. length. It surprised me by shooting 1 hole 3 shot groups.(Speer 75 grain HP on top of 25 grains of IMR 4895.)It had moderate recoil and primers were did not show pressure. Moving load to a Speer 100 Grain Spire-point. and 24 grains of IMR 4895. Should be interesting.
It’s been consistently about $2 per round for a 6mm rifle while I can get 5.56 rounds for about 70 cents a round or less. Doesn’t make any sense.