https://bcprecisionballistics.com/
https://youtu.be/UqfpMxci168?si=YgXwwpik9wt3kGC1
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A propriety cartridge, from a boutique developer, with 100 FPS MV - which is less than 65 yards diff for equivalent ballistic performance - over a SAMMI cartridge, with the provenance of Hornady, and market momentum behind it?
No chance it achieves anything beyond being an interesting novelty that pops up on occasion…if that.
If we’re playing this game why not 6mm Grinch?
Does it make a difference that 6mm Max uses standard AR15 bolts? Parent cartridge is 350 Legend. Seems pretty legit to me; all the performance charts show chamber pressures at or below 54k PSI.
ETA: The video does mention that 6mm Max is going through SAAMI testing right now.
All the benefits of using a 5.56 bolt are great.
However, 6ARC is a DOD selected and procured cartridge which means for better or worse it isn’t going anywhere.
Does that mean it has to be broadly accepted by the US civilian market? Chances are we’ll never see any USGI 6 ARC stuff anyway.
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As far as adoption goes, it hasn’t been widespread, if at all. I don’t doubt at all that some units are fielding them, but we’re not talking about 30-06, 9mm, .45, .308, 5.56, or even 6.5x55. Maybe we’re talking about 6.8spc, maybe not.
Its a cool cartridge, though. A lot going for it. All the same stuff that’s going for the topic cartridge, but that one can use TDP bolts.
An entity within DoD procured 6ARC ammo from Hornady, guns from Barrett, and suppressors from OSS/Huxwrk. Was it a POR, NPOR, unit purchase, or ??? Is there an existing IDIQ contract that ensures ammo and spare parts flow, or will 6ARC fade as budget priorities move on? I don’t think 6ARC’s future in the DoD is at all assured, let alone in the civilian marketplace.
From what little has been published, it sounds like ARC was developed for a specific unit and may have been sort of a one time deal. Hornady and others hint that it was a special operations unit but I suppose to could have been AMU for all we really know.
The 6.8 didn’t live up to the hype but it and the Grendel, if nothing else, helped create a pretty active AR wildcat market.
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If 6mm MAX brings 6ARC type performance to a rifle using a 5.56 bolt, that’s a pretty big deal. I’ve been shooting and loading 6.5 Grendel for nearly 20 years and 6mm MAX has my attention in a way 6ARC never did.
Pardon me, but why? You’ll still need specialized magazines. What’s so troublesome about using a different bolt head?
Because 6ARC is too similar to 6.5 Grendel to bother with it. 6mm MAX using the 5.56 bolt is very interesting to me, and we’ll see how the bottlenecked rounds stack vs the parent straight-walled cartridges. The Grendel/ARC case taper does not help with stacking in AR mags, hopefully MAX does better.
Using the 5.56 bolt is a bonus, to what end, however?
I’m not denigrating the round, I think it was a great concept when it was done before (.22 Nosler pops into mind), and I think it is a great concept now, but I also don’t think it matters much.
It doesn’t allow the AR-platform to operate at bolt-gun pressures and the vast majority of casual end users - who are needed to move the needle in the marketplace to elevate the round out of the ‘novelty’ arena - could not possibly care less. It isn’t difficult to find any of the various sundry bolts to run any standard cartridge in a small-frame AR anymore. Plus, what drives market success is ready availability of complete firearms with consistent ammo and brass availability.
One only needs to cruise the end-user online platforms for a short time to discover the most significant ‘problem’ with the ARC - ammo and brass availability. If the comparative manufacturing monster that is Hornady can’t meet consumer demand for a product it put a significant portion of the reputation of its brand behind, how will a smaller and relatively unknown developer avoid the same fate with a completely different concept?
Again, a great concept…but will it matter to anyone other than niche users?..and, if not, how long can it last?
SOLGW is making barrels and complete guns… And they’re shooting for $1.50/round for loaded ammo, which is comparable to ARC. I’m kind of excited for the round because it’s just a barrel swap and maybe a few 350 Legend mags to convert over, and it uses the same powders as Grendel.
I do agree it’ll be a niche cartridge, but that’s just fine with me. I still think Grendel is a niche cartridge and I shoot it a lot. Grendel had a moment when Wolf steel cased ammo was $6/20, but those days are an unprovoked invasion behind us now. Maybe AAC making Grendel ammo will make a difference.
Durability.
The 6.5G/6ARC bolt head walls are incredibly thin (as is the extractor). By increasing the bolt wall thickness you’re increasing durability/ longevity of the bolt and extractor. Most people who’ve shot more than a few thousand rounds of ARC have seen a bolt failure or two. If you look at the barrels out there, most gas systems are far longer than seen with other cartridges for a given length, to attempt to reduce pressure on the bolt. We all know bolt life is an issue with 6.5G and 6ARC.
Using a thicker walled bolt and thicker extractor while pushing a nearly identical projectile (for basically the same or better performance) is a major way to guard against a rifle going down hard in a match (or worse). 6ARC was never meant to be for everyone, and neither is this… but folks who’ve shot enough ARC to break a bolt or two are probably paying close attention to see where 6 MAXX goes. It has a lot of potential, it’s just a question of how well it catches on and how available/ economical it can get as adoption of it grows.
I acknowledge that your new cartridge outright avoids the problem, but I don’t know why industry standard for 6.5 Grendel and 6mm ARC hasn’t moved to a stronger bolt and barrel extension design within the same envelope, like Knight’s has.
Doesn’t Ruger use a proprietary bolt in its 350 Legend rifles? I assume it is something similar to the bolt in the SFAR. I’d think something like that would be a good way to get around the weakened bolt face.
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Myself and a bunch of other Grendel shooters didn’t get that memo. 
I wonder if ARC is running at higher pressure?
I’ve got multiple thousand rounds on one and never had an issue. Maybe not 5k+, but easily 2-3k.
I have seen one broken extractor on a new 6.5G bolt after ~100 rounds that I attribute to a manufacturing issue. Still should not have happened.
Bolt thrust is a real issue and why the Grendel isn’t hotter than it is. If the max can run at much higher pressures with the rebated case head that could be an advantage.
I might be misreading this but I don’t believe a rebated rim can reduce bolt thrust.
You are correct, bolt thrust is based on the internal case head size and is independent of rim size.
What I was trying to say is perhaps the new cartridge can run higher pressure due to more meat on the bolt.
If it is not rebated and is no larger diameter than 5.56 I don’t see how they’d have enough powder capacity to beat most of the other beyond 5.56 cartridges.
My understanding is that both grendel and ARC need to run at 52k psi because of bolt thrust limits. Both can be loaded hotter with the risk of bolt breakage.
I don’t know enough about the new cartridge to speculate so will go back to listen mode.