6mm WOA. If you load I think there's been a couple 6mm variants on the 6.8.

brownells has them for pre-order.

I saw those, and I'll be ordering the 18" version once I get moved into the new house in a couple weeks.

Half a millimeter is .02" --it may well be possible (not suggested or wise, but possible) to swage a soft bullet that much.  Better shot than .08" in any case.

The alexander mags are the best in the context of grendel mags. I dont think I've had a grendel mag that hasn't fucked up. I've yet to have one I would trust.

Ask zander about all the pictures I've sent him of my mags failing and me throwing them across the desert.

It would seem to me, this will not take off if no good magazine exists.

lol I believe it

Yet the Grendel has done great. When people want something to work they stick with it. The gun world is weird that way. Products that in other industries would get abandoned almost immediately stick around for a decade because of the die hards.

From experience with coyotes seems to be that speed kills. I shoot 204 ruger now and have relitively good luck with it. But having a extra 15 20 grains of bullet will be advantageous. That and the weight and cost of building say a 22-250 or 243 in ar10 vs almost anything in ar15 is significantly less is all my reason Im excited for this round. Im not saying its for everyone just fits my niche is all.

While I'm not disputing the success of the 6.5mm Grendel, It still seems (to me) that there is a split in opinion as to what is the "go to" mag for reliability.

And I assume that will cary over to the ARC.

I would also assume the New Barrett Rifle that SOCOM  is accepting, must have worked that problem already prior to selection.

I've always been a 5.56mm purist, but I have three AR's and I wouldn't might converting one over to a different caliber as a long range Precision Semi Auto.

But much like VHS vs. Beta, I don't want to pick wrong. I know 6.5MM Grendel has a lot of time and support, but there is just something about the 6MM ACR  in my gut,that tells me that it will be THE go to rd and surpass the Grendel.

So I'm going to have to sit on the fence for awhile.

Sorry for the abbreviated reply coming, today is busy!

Re: .22 v .243 barrel length efficiency

- Axiom 1: the larger the bore, the more efficient burn in shorter barrels, given same case capacity (tinkering with modern powders can offset sometimes, let's stick with factory loading for apples/apples). That's why 6.5mm is even more efficient.
- Axiom 2: if you need the long, heavy bullets, you should drive with a long barrel to get the performance up. If you SBR, you should go with a lighter bullet to recover short-mid range velocity/performance. For general example, using 190 in a 16" .308 does not help you at mid ranges - you want a 155 for that application.

- .224V: This guy went down to 16.5", 2550fps 90gr. Still not SBR testing, which is what my essay from a couple years ago states as a key to the next all-around AR chambering niche. They did not hit the decay part of the curve in that test, which is interesting. If going down to 12" gets us to 2400fps with a 90gr (VERY optimistic IMHO), then you have the associated wind drift performance. In standard atmosphere, that's about 35.2 MOA 10 mph drift at 600y, 0.950 sec TOF.

- 6mmARC: earlier someone posted a chart showing 2350fps with a 108gr at 12". In standard atmosphere, that's about 35.4 MOA 10 mph drift at 600y, 0.967 sec TOF.

- That's essentially identical wind performance between the two most "common" bullet weights for the cartridges. With the assumption that the .224V velocity doesn't completely tank at 12". There is a significant weight difference, however. The real "shine" for SBR is when you put mid-weight low-drag high-terminal performance bullets in....to get the velocity up. Shooting slow bullets in variable conditions ABSOLUTELY SUCKS. I would love to see testing data on 100-105 class 6mm bullets. Not sure what the right solution for .22 is yet, but I am not optimistic that manufacturers will start cranking out a bunch of well-engineered .224 bullets all for a single cartridge.

- Stabilization issues. 90gr is on the top end of .224 bullets, more difficult to stabilize with shorter barrels and lower velocities. Forgiving with SBR, temperature ranges, and air density changes? Only lots of testing knows for sure, but likely more problematic. Much easier to stabilize a 103gr 6mm bullet in a short barrel under wider conditions.

- Barrel life. Somebody brought it up, but basically a 103gr load in a 6mm will kill the throat a LOT slower than a 90gr .224 bullet all case capacities being equal. The guys shooting the 6mmRAT/Turbo40/whatever are getting really long life out of match rifles, which see hard throat use with string fire.

- Bullet selection: any good hunting/kinetic performance bullets in general circulation for 90gr .224?

So.....basically for all the reasons I stated a couple years ago, 6mmSomething is still the ticket for wide adoption in the AR platform. Not convinced the 6ARC is it, but it's a step in the right direction. Maybe in 2022 we all need to buy the next one.....

Also....if you NEED to shoot 1000y out of a semi platform, why would you not use a full-length, full size AR10? With the correct chambering? A longer-than-carbine AR15 platform has no business off the square range with a can on the front. The market we are talking about here is a 11-16", suppressed, mid/light-weight, AR15. 0-600y. 800 at a stretch, and you won't be competitive with the 20-26" AR10.

Because it's more profitable to sell people the next wonder cartridge

Gun university, Cleckner used the rifle DOD requested. While this review was for the round not the gun his biggest complaint was the mags. Shocking.


Article.

Reamers are one thing that screwed the Valkyrie out of the gate, along with support for a very thin projectile in a short case being cycled through a gas gun.

One thing you would notice is that it shot amazingly well from bolt guns, but then multiple high-end shops had trouble getting it to shoot from AR15s.

These are shops that regularly put out AR15s that shoot phenomenally well in different chamberings, mainly .223 Wylde and 6.5 Grendel, including JP and Precision Firearms.

PF said he had to have his own reamer spec'd for the 90gr SMK loaded at mag length 2.260" COL, and then they started shooting.

JP eas experimenting with all kinds of reamer designs as well trying to get it to shoot.

I said from the start, "Why are they messing with this when they could be doing a factory .224 or 6mm AR?"

There's also something to be said about cup and core bullet jacket uniformity and concentricity deviations becoming a bigger challenge when going to the .224 bore, so you really have to have tight QC on the projectile production line once you go that small.

Once the projectile gets run through a gas gun action, especially with really soft brass, chances of concentricity runout increase, leading to improper projectile hand-off in the chamber, especially if you tried to make the chamber handle both the 90gr SMK and a shorter hunting bullet with a tangent ogive.

LRRPF52 I’ve seen you post a lot about the Grendel, and the information has been extremely valuable. Especially when I was looking to build my Grendel with a 16” barrel and wondered if I was essentially neutering the cartridge. My question comes in with how the two cartridges compare in the real world. I’ve read a few articles comparing the 6mm ARC and 6.5 and all of them seem to tout that the 6mm is flatter with less wind drift, and the 6.5 maintains a little more energy at range. Maybe I’m using my ballistic calculator incorrectly, but every combo I use of comparable BC projectile and barrel length has the 6mm overtaking the 6.5’s energy within a few hundred yards. I’m a self proclaimed Grendel fanboy and love the cartridge, but if this new offering outclasses it on every front, I may be swapping in the future. I do love the ability to shoot steel cased ammo, but my Grendel was built more as a deer popper/possible long-ish range target rifle than budget blaster. Any input you could give would be much appreciated.

What length barrel are you guys running? And for what branch?

Because of the velocity and high BC, the 6mm cartridges based on 6.5 Grendel will have comparable energy on-target at certain ranges when same barrel lengths are compared.

There should be a point at distance where a high BC 6mm overtakes a lower BC 6.5mm, especially since the muzzle velocity is roughly 150fps faster between a 6mm 105-108gr, and a 6.5mm 123gr.

The first impression for me shooting 6mm AR is how the recoil is like shooting a 90-100gr in the Grendel, but with flatter trajectory and less wind.   If you don't want to make a lot of adjustments to your elevation turret, there isn't a better LR cartridge that fits inside the AR15, and it's also the one to beat for wind deflection.  There are several loads in 6.5mm that retain energy a lot better than others, like the 123gr Scenar, 123gr SMK, 130gr Berger AR Hybrid, and 130gr Nosler RDF, which is competitive for wind drift.  MV is just slower with those bullets compared to the 105-108gr class in 6mm.

For a hunting round though, there is currently one factory 6mm ARC 103gr ELD-X from Hornady.  Will Barnes, Federal, Nosler, PPU, Remington, Sellier & Bellot, and Winchester jump on that wagon?  I can see the usual smaller shops who target PRS getting onboard with it soon with more target bullets.

6.5 Grendel has a boat load of factory hunting loads, out of over 90 current factory ammunition options for it, with hundreds of sources for ammo on ammoseek and in major online retailers.  I think it's safe to forecast that 6mm ARC will not achieve the number of options for hunting ammo as 6.5 Grendel currently commands, given what is is designed for.

Both will kill of course within reasonable distances on medium game.

Ammo availability favors 6.5 Grendel substantially and will into the foreseeable future.

I definitely will agree on the effectiveness of the Grendel on game. Turned a buck’s lungs to soup last season. Thank you for your reply.

I built a buddy a 6x6.8 for hunting. We get 55gr Vmax just over 3400fps out of a 16” barrel. Think of that. Turns big ole jacks into pink mist.

Super easy wildcat, just simply a necked down 6.8. The ARC has the edge for long range target shooting because of its shorter case allowing long high BC bullets, but for hunting applications, the 6x6.8 will beat it for speed with sub 100gr projectiles.

I also have a 25x68 I just started playing with. Also for hunting not long range steel.

I just ran the internal ballistics through a custom Grendel-based cartridge Powley computer model.

It has been within 10fps on all actual mv readings I've done personally when estimating muzzle velocity change when you manipulate the barrel length and bullet.

I input the 6mm ARC 24" barrel mv with a 108gr, using 32.1gr of powder.

Changed the barrel length to 16" and bullet weight to 55gr.  

Predicted velocity:  3439fps

52 vs 58k of pressure. We’ll see. I’m not knocking anything, just skeptical lower pressure and lower capacity will result in the same velocity.

Lower pressure with more efficient combustion chamber resonating the burn rate back towards the point of ignition with 30° shoulder would account for that.

55gr sounds great for closer range p-dog blasting.

87gr V-MAX (.400 G1 BC) and heavier would make more sense for coyotes who are really skittish already.

I think I would still shoot the target bullets for yotes, no real reason to go lighter if you can get a lot of trigger time with a common load.

It's a lot better than .223 Rem.

If we're talking 3400+fps up to 100gr +/- bullets, isnt that in the 243 Win category of velocity/performance?

3400 would only be with really light bullets not 100+ grain bullets.

That's why I included "marketing" in my post --he definitely put in a lot of legwork to promote a cartridge concept that wasn't the most original idea, though I'd argue that pitching the 6.5PPC to the US military as an infantry rifle/lmg round was pretty novel.  It may have existed (because every wildcat permutation of every case head already exists) but it was obscure by any standard, lost in a sea of a half dozen other PPC cartridges that trace back to 7.62x39 if not farther.

The other requirement is the round can't be 6.8SPC, for the shitshow reasons already mentioned.  I had no idea that cartridge was such a political dumpster fire.  Where's seppuku when we need it?

I enjoy seeing the discussion the new Hornady offering generates.  Lots of different ways to skin a cat.

I cut my teeth on long distance shooting with the 6.5 Creedmoor.  At the time I bought the Creedmoor I was learning how to shoot to further distances.  The allure of the Creedmoor was that it offered more performance to make up for my lack of skill.  So, mistakes that I made with the .308 or 6.5 Grendel weren't as severe when shooting Creedmoor.  As my shooting improved, so did my love for the Creedmoor because the gun was just so accurate, even with my mediocre handloads.  I figure I'm about halfway through the life of my Creedmoor-barreled DPMS, and it took me about eight years to get there.  I still have several years left in my current barrel unless my shooting volume increases.

One thing that excites me about the new 6mm ARC round is the performance one gets relative to cost.  Yeah, it's going to be more expensive than shooting 5.56, and it won't offer the performance of my Creedmoor, but it seems like it strikes a reasonable balance for those of us willing to endure the cost for accuracy at distance.  I could add a Grendel to the stable and shoot steel case for a quarter a pull, but odds are I wouldn't be happy with the accuracy one typically sees with that load.  It boils down to where one wants to make trade offs.    

One disadvantage of the 6mm ARC to me is bore size--I have a .30 cal can, but it's physically larger and heavier than my .22 can.  For that reason I'd still probably lean toward the .224 Valkyrie slinging heavy-for-caliber slugs rather than the 6mm so I could stick with the smaller can.

So it's better than 5.56 because of heavier bullets, and it's better than 6.5 because of lighter bullets?

I'm gonna hold out for the 6.35/.25 Grendel, it will obviously be better than either 6.5 or 6mm.

So should I buy one or not

I want to see a magazine that is reliable.....until then, not going to jump in.

Valkyrie ain't looking so bad now huh

Tag to keep thread alive and hopefully get some actual user inputs...

Hornady 6mm ARC Cartridge - What You Need to Know