SAAMI Approved: 6mm ARC
 

SAAMI just published drawings for the “6mm Advanced Rifle Cartridge.” It’s a 6.5 Grendel (7.62x39mm, 220 Russian) case with the shoulder pushed back, taper slightly increased as the shoulder diameter is the same as the Grendel, and naturally, necked down to 6mm.

SAAMI Drawings for 6mm ARC

Speculation is that Hornady is involved (wholly unsubstantiated at this point), as a major driver for pushing the shoulder and neck back MIGHT be to accommodate long ogive, heavy for caliber 105-115 class, high BC bullets like the 108 ELD-m, but still remain within COAL maximums for AR mags. Early speculation also expects it should run somewhere around 2700fps with the 108 class bullets, giving it considerably greater super-sonic range, with less drop and drift than the 6.5 Grendel parent.

Some folks might recall my enduring lust for a few years for a 6mm Grendel variant, and that I finally built a 243 LBC last year. I’ve long considered a 6mm Grendel to be about the ideal mix of speed and bullet weight from the 2.3” class of cartridges, and I wrung my hands for about two years because I didn’t want to be locked into any single source, proprietary cartridge. This cartridge will have slightly less case capacity than the 243 LBC, so I’d expect it to give up around 100-150 fps to the longer LBC (or doppelgänger 6mmAR). The 108 ELD’s tend to run considerably slower than I can push the 105 Hybrids, which I push to 2900 with the LBC case, so I’m thinking 2700 with a 108 ELD seems pretty reasonable. I’ve considered the 6.5 Grendel/6 Dasher/6 Creed/243win class of cartridges to be optimum for deer hunting, and this entry into that class will be fantastic for sport shooters and hunters alike.

I’m thoroughly excited about the prospect of a CZ 527 Varmint Tactical in 6mm ARC in the near future!

Ya gotta post some pictures man. I'm already drooling.

This sounds interesting. 6mm seems to be that sweet spot in cartridges.

I wish I could do better, but the only solid info I have on the new 6mm ARC is the SAAMI drawing page I linked above.

I think I’ve shared this photo of my first dummy round for my 243LBC here before, but this would ROUGHLY approximate what the 6 ARC will look like - only a little longer. This is a 105 Hybrid seated to mag length, and you can see there isn’t much bearing length left before the ogive would slip into the case mouth - which is why I suspect the SAAMI submission, whoever made it, includes a pushed back shoulder compared to the 243 LBC pictured here.

A post over at the Hide is suggesting Hornady is, indeed, behind or at least involved in the submission.

That ought to help things along. Hornady has a good rep for this kind of stuff.

Scuttlebutt: the SAAMI approval came late in Jan, and things weren’t ready to drop at SHOT. Now, with the CV economic dip, school closures and job losses, and social media sensationalism of it all, Hornady is parlaying launch until we can step outside to confidently breath fresh air, and have some money to spend.

Since it’s so very close, but a step smaller than my 243LBC, I’m not sure I’ll buy a barrel when it does drop, but I do expect, eventually, most barrel companies will simply stop making the 6mm Grendel Wildcats in favor for the standardized cartridge. That day, I’ll cry over 50-100fps, buy a new barrel and dies, and party on happy.

Well the cat’s been all but fully out of the bag for some time now, as we’ve seen brass, reamers are for sale already, and it’s all but officially announced...

Well it appears we won’t be waiting much longer, as Hornady dropped their teaser video promising to satisfy our curiosities next week:

Interesting Twist
 

Well the cat’s fully out of the bag now. What I found interesting in the Hornady announcement is that they developed the 6 ARC after a DoD request for a replacement to the 308, fitting into the AR-15, for some unspecified application.

It’s also looking like the velocity spec for the 105 and 108 factory ammo is a bit better than previously expected. 2750fps with the 108 ELD is no joke - transonic boundary past 1250yrds! I’ve had the 108’s out to 1400 when pushed to 2900 - but I was burning 10grn more powder to do it.

https://www.hornady.com/6mmARC#!/

They state right in the promo materials they used a 24" barrel to obtain those velocity figures.

To me, as a guy that is mostly from the military/tactical arena (I'm ex infantry), this round is a solid blah.

Data is out already showing 2450 from a 14.5” barrel. Not bad speed at all for an SBR, cannot complain about a 14.5” rifle with a transonic boundary past 1,000yrds.

That's swell and dandy but I see no particular military application for that. This is a round that was developed for/by DoD.

M855A1 is traveling at 3000fps from the same barrel length. In the thinking of the military M855A1 is already insufficient in armor penetration, which is why the Army and Marines have the NGSW program and these super hotrodded unicorn 85k PSI 6.8mm rounds competing. What is the point of a 2450fps cartridge from a 14.5" barrel in any kind of a military context?

None that I can think of.

If this is in some way slightly better than some existing cartridge in some niche hunting role or something, that's great. I see it's military value as somewhere slightly north of zero.

what would a 30rd ar15 5.56 mag hold in 6mm arc? single stack? 10-15?

seems appealing for an ar15 setup

in a bolt gun, not sure I see the appeal.


found my own answer....supposedly a 30rd ar15 5.56 would hold about 25 6mm arc.

Yes 25rds, same as the largely defunct 6.8mm SPC.

Guess it’s a good thing the DoD didn’t ask your opinion, since they obviously had an application for the 6mm ARC.

I wonder what would even make you hit your reply button and type that.

Is it ok with you if we discuss the merits of this cartridge in a military context? Your comment is entirely unhelpful...you did not even begin to offer any kind of information or debate, just a snooty remark.

What is it that you (or anyone) foresees this doing in a military context that existing cartridges do not do? Outside of being cheerfully accepted by a few guys at Camp Perry, I see none.

But I'm just a former Mechanized Infantryman, so what do I know.

If you can’t understand any potential military applicable advantage of firing nearly twice the bullet mass with considerably higher sectional density (.25 vs .18) and twice the ballistic coefficient, which reaches 600 yards with 400fps greater velocity and 3 times the energy than M855, I don’t expect we can have a fruitful discussion.

What we do know - the DoD asked for this type of performance and such was delivered. So someone with a much more important opinion on the matter than you or I sees value in it. Barrett has begun delivering 18” Rec7’s with Proof Research match grade barrels to the DoD, so I think it’s reasonable to speculate your average infantryman isn’t going to be handling them - it’s obvious this isn’t a replacement for the M4.

I understand it will have significantly more recoil, and the magazines will hold 5 less rounds, thereby meaning an individual soldiers load out will be 35rds smaller. I understand the ammunition will also be significantly heavier.

I further understand that introducing a new cartridge will complicate logistics and supply chains.

In a military context these things matter far, far more than the ballistic coefficient of a projectile.

There are squad designated marksmen in every US squad, so this is potentially very relevant even at the infantry squad level.

Also, the US Army NGSW program calls for super hotrodded cartridges that push the envelope of technical viability (Sigs 6.8mm 85k psi round being a prime example- I believe the civilian designation is .277 Fury). Is this a fall back position if the NGSW fails? Does the military see it as a potential re-chambering for 7.62mm M240 machine guns? These are all 100% viable questions, and they are all directly relevant to the infantry.

Or is this a new sniper round. In which case, why are we even comparing it to 5.56mm ballistics at all? In that case the proper rounds to compare it to are 6.5 bleedmore, 7.62mm NATO and .300 win mag, all of which the military is currently using in that role.

As far as important opinions, the DoD asks for all kinds of, quite honestly, idiotic things. At great tax payer expense. Which is another valid reason to question this round, considering that we are in the middle of an economic melt down and the Pentagon is sure to see greatly reduced budgets next year. And we are all tax payers here.

Finally, I would say the bottom line of a discussion forum is to discuss things. Not for one dominant grouchy old buck to try to shut down conversation, for reasons known only to him. I am pretty sure that is not how any of this is supposed to work.

Also, what role would you or anyone else see this round filling from a hunting perspective? What does it do new, that some existing round is not already doing?

The DoD is far and wide compared to the limited scope most people complain about in rants about logistics. Various groups have been making use of a great number of cartridges for a long time, which has had absolutely nothing to do with the typical infantryman.

But the origin is what it is - the DoD asked, Hornady answered, and luckily for us consumers, a great little cartridge with almost almost 20yrs of wildcatting behind it - arguably nearly 50 years - is finally available in a low cost, factory offered form.

What are the cartridges that DoD Has been using for a long time that have nothing to do with the infantry? The only one I can think of off the top of my head is HK 4.6x30mm, which the USN uses in a suppressed role for sentry elimination (allegedly, even if it does seem a very peculiar choice)

One thing I think we need to consider from a military context is that if an EPR style penetrator projectile is used, maximum projectile weight will be in the area of about 85 grains.

I am interested to know what you think the ideal civilian hunting applications are. Seems like it would be pretty good for people who want to hunt big game (mule deer, etc) at longer ranges with an AR15 style platform. I think it has more promise as a civilian round, to be honest.

Sure is a good thing Hornady released it into the civilian market then, ain’t it?

I made my support for the 6mm ARC as a hunting cartridge clear in the original post:

I found this today as well, relating to the various barrel lengths which will inevitably be used.

You seem combative. This is like the 4th time you've responded to me aggressively for no apparent reason. Is it cause i'm the new guy, or because you're not used to anyone questioning you here?

Saw it reported on TGC news today the 6mm ARC is claimed to have 54% less recoil than 308, but 73% more recoil than a 5.56mm.

This isn’t a military forum, and this wasn’t a “the military plans to replace the 5.56 in the M4” thread, and such was never implied. But you’re a hammer which only sees nails. There are more functions within the DoD than infantry, and they issue a lot more than 5.56 M4’s. You could have simply left it at accepting that. But instead you’re wasting your own breath being dismissive about a new COMMERCIAL cartridge because you don’t see it as an advantage over the M4 in 5.56 for infantry use. No one has said it is meant to replace the 5.56, but you seem to insist on banging that particular drum.

If you had anything to add to this discussion regarding commercial sale, civilian use, and didn’t focus only being so dismissive regarding your imagined proposal for this as an infantry rifle, and maybe if you didn’t insist on so much of your own snark, I would be more inclined to take you seriously, and would be less inclined to point out the foolishness you’re bringing to the table.

I did not realize it is forbidden to discuss the military applications of a military cartridge on a discussion forum.

As far as "imagined" proposals, many commentators in military circles believe that this cartridge is a hedging of the bet for if (when?) NGSW- which is a tremendously ambitious program- does not work out. Which would potentially thrust 6mm ARC into a prominent infantry role.

Furthermore, the title that you selected for this thread does not in anyway indicate you wish to only discuss it's utility as a civilian cartridge.

I think you are just making excuses for being so cranky. ;)

I have been thinking about this more. What about an infantry squad composed as follows:

Standard riflemen: M4 or M4A1 in 5.56mm
DMR: Updated M16A5 or Mk12 SPR in 6mm ARC.
SAW: M27A2 rechambered for 6mm ARC with Magpul D60 drum magazine (which would probably hold 50rds of 6mm ARC)
Platoon level machine guns: New belt fed gun in the 13-15lb range chambered for 6mm ARC.

I am coming to see this as a viable universal support weapon replacement caliber, the more i think about it.

Hornady trickled out load data for gas guns last week, and released this week bolt gun data, for bullets 58-110 grains:

Hornady 6 ARC Bolt Gun Load Data

From a military perspective, the 5.56 has left something to be desired over in the sandbox. There are plenty of published articles regarding this. This issue was a lot of what drove the 6.8 caliber development. I wasn't as impressed with the 6.8 ballistics although I can see where it might have some specialized uses. A 6mm now, is kind of like a beefed up 243. From the info NoMercy posted, it seems like this 6mm ARC has been designed to have more punch at longer range than a 5.56 would. Personally, I'd love to have a 243 in an AR-15 platform. I'd gladly give up a few rounds in capacity for a round that has a lot more punch and range. As an ole jarhead, I think a platoon of Marines carrying M4's in 6mm ARC would be quite lethal in the sandbox. I don't know if you'd want a machine gunner using that caliber or still using .308 as I haven't considered that all the way through. I do know I'd be a lot happier carrying an M16 variant in 6mm than I would in 5.56 for any longer distance combat arena.

On the civilian side of things, it's a new cartridge, has load data from Hornady and stays supersonic way past 1,000 yards. I can see this round catching on. :patriot:

It has always been a compromise between the number of rounds you can carry and the effectiveness of the cartridge. The newer AR platforms seem better at mitigating recoil so a little more oomph is practical, But it goes back to how much weight and the number of cartridges it is practical to carry. A basic load for a rifleman is a little over two hundred rounds.
The M 249 is IMO way underpowered for a squad weapon, improving the energy of the round would be a plus.
The technology has improved significantly over the years, but physics has remained much the same.
How many rounds you can carry, the energy of the projectile, the weight of a basic load and recoil. A weapon that can be fired from the hip or underarm has its advantages or basically something that can be fired on the move without, having to stop to shoulder it, breaking your forefinger, and(or is relatively controllable.

Personally I've always favored bigger is better. A 7mm would make a better S:A:W: but would weigh down a normal rifleman and limit the number of rounds he (or she) could carry. There is something to be said for a S.A.W. and a rifleman sharing the same caliber ammo. Have you ever tried to stop a truck with a squad MG? Way more difficult than you'd think it isn't like the movies. Inflicting casualties isn't the only consideration. Stopping light-skinned vehicles or even airplanes is a part of the mix.

As a hunting round IMO the 6mm ARC doesn't bring anything to the table some other rounds couldn't do better. Doubtful the ammo weight would be much of a factor Side note an overpowering hunting round doesn't do a lot of good, much of a bullets energy is wasted if it passes all the way through an animal. Too much velocity often just wastes meat or destroys pelts, bruised and shredded meat is a waste, exploded Varmints are useless.

I can see where the 6mm ARC would be a step up from the 5.56 as a basic infantry round. A more powerful round is needed in the Middle East. As for the M249, I couldn't agree more. 5.56 is way too light for a SAW.

I agree on the SAW. It should be 308 or even something with a little more oomph for when they need it.

Fun FYI update on real world performance: I’m squadded with a couple Hornady engineers at a National Rifle League national level match this weekend, both shooting 6mm ARC in custom bolt action rifles. One is running a non-canister powder which is used in their factory ammo and one is using Leverevolution - they’re getting 110 A-tips up to 2900fps! I’m shooting a 6 Creed at the top end of the NRL/PRS speed limit with 105 Hybrids, and we’ve been within 2 tenths wind hold clear out to 1175yrds. I had a chance after the stages today to test drive both rifles, a Bighorn and a Mausingfield (opened bolt face), and the recoil compared to my Creed is notable - even a rifle 3 pounds lighter than mine had considerably less jump when shooting free recoil on the barricade - about half as much reticle travel. Very similar performance to 6mm BR/BRA, but with far less expensive brass. They mentioned 7 firings on the brass they were shooting today, but they said they’re not sure how far it will go - they’re getting it cheap enough they simply replace it after 15x fired.

I had been planning a 6mm creed for my son, and a 6.5 Grendel upper for his AR, to allow him to shoot factory ammo. But with the 6mm ARC on the market now, I’ve ordered a 6mm ARC barrel for his AR instead of the Grendel, and after today, I’m thinking very hard about building a 6 ARC bolt gun instead of the Creed. I also ordered two 6 ARC barrels to replace my 243LBC Barrel this winter when it’s burned out.

Both guys were running factory MDT 12 round AI pattern mags with BR blocks. Feeding was smooth and reliable, even when I ran the rifles, with a VERY different habitual bolt throw than their actions (mechanical ejectors on theirs, cock on close spring ejector on mine).

It is tempting to build a bolt rifle using this cartridge. I am not quite sure if it would fill a need for me but it might be a relatively inexpensive cartridge to punch paper on noncompetitive range days. I would imagine that barrel life will be fairly long. Only time will tell if this one hits the sweet spot in the market and becomes popular with civilian shooters but it sure looks like a great idea.

I wanted to post this over the weekend but couldn’t recall my Flickr login info to host the photo. But here’s a side by side comparison with my 6 Creed. I’m shooting 105 Hybrids over 41.9grn H4350 running 3163fps from a 26” barrel (which is ~80fps faster than this same load produced in my last two barrels), pictured here beside his 110 A-Tips over 31.5grn Leverevolution (slightly over book data, bolt gun only, no AR’s) at 2900fps from a 28” barrel. One of the Hornady shooters in my squad running the ARC placed in the Top 10 at the NRL match this weekend, which he said was his highest placing to date, so it obviously kept up, despite vicious winds and an intense course of fire.