6mm ARC availability

[COLT45SA]

I really like everything I've read about this cartridge, and would even like to have a rifle built for it. But to date, when I go to local shops and gun shows I have yet to see ammunition or components for the caliber offered for sale. Is the caliber a "flash in the pan" or is it here to stay~?
Ten years ago I got into the 6mm PPC and really enjoyed the experience. Today finding brass for the PPC is an impossibility, and I'm concerned that the same fate will fall on the 6mm ARC.
Thoughts~????

 

[Kracken McGraw]

With the Hornady marketing team behind it and the fact you can make cases out of Lapua 6.5 Grendel brass, I’m pretty sure it’s solid.

 

[KaiserNorton]

Like everything else right now, it is scarce. When the cartridge was first announced, ammo was pretty easy to find, though unprimed brass/reloading dies were not. I think as the shortage lessens, it will become more easily located. And as Kracken states, with Hornady behind it, it is unlikely to disappear from the radar....

 

[6bra1k]

do not know where you are looking but in the middle of this massive run/shortage i bought 200 pcs of lapua 220 russian no problem.
as far as the ar,i see no future other than "its new , i want to try it". its death kneal to me was the 50kpsi number for max.

 

[10XSHOOTER]

Saw 6 arc ammo at Sportsmans in Casper, Wy last weekend.

 

[North Fork]

You mite want to look at the 6XC

 

[Bill K]

Until brass starts showing up and you can reload for it. Get some 6.5 grendel and form it.

 

[SD guy]

Been a long while since I have seen 6mm ARC ammo in a local store. May have a lot to do with I have not been looking either. See lots of the three choices on line though. Prices are higher than I stomach well though.

Think I bought 8 boxes or so last fall. I have formed another 100 pcs of brass from Lapua 220 russian and another 100 from Lapua 6.5 Grendel. case capacity of all 3 seems remarkably similar. I feel the Lapua brass is a real step up in quality.

In terms of accuracy for my shooting capability with my light weight rifles I notice no difference from the small flash hole Lapua to the standard Hornady 6mm ARC fodder.

 

[gunsandgunsmithing]

Until brass starts showing up and you can reload for it. Get some 6.5 grendel and form it.

..or use 220 Russian. Just form a false shoulder to set headspace then fireform in the ARC chamber. Can't remember if it'll need trimmed for length or not without looking. The only potential issue with using Grendel brass is neck thickness, especially after necking it down. Of course, that'll be dependent on both the brass and the chamber dimensions. I bet you could also use cheapo 7.62x39 brass too, after necking it down and putting the shoulder where it needs to be, then fire form it in the chamber.

 

[CJ6]

do not know where you are looking but in the middle of this massive run/shortage i bought 200 pcs of lapua 220 russian no problem.
as far as the ar,i see no future other than "its new , i want to try it". its death kneal to me was the 50kpsi number for max.

While the 52 kpsi is most likely the "factory" gas gun loaded pressure, Hornady's book also has 62 kpsi load info for bolt guns.

 

[6bra1k]

While the 52 kpsi is most likely the "factory" gas gun loaded pressure, Hornady's book also has 62 kpsi load info for bolt guns.

ok tell me what is the saami spec ???
it should have been 60 or 62 to begin with. my guess is someone bowed to the mil rather than request they move into the modern world.

 

[CJ6]

ok tell me what is the saami spec ???
it should have been 60 or 62 to begin with. my guess is someone bowed to the mil rather than request they move into the modern world.

According to Hogdon SAAMI is 52 KPSI....Their "Bolt gun info is for "higher than standard SAAMI 62 KPSI" not to be used for AR/Gas guns.
edit to add ....The pressure limit 52K really makes no sence because 5.56 NATO is loaded to 60 K and used in the same AR/Gas gun platforms.

 

[204 AR]

The pressure limit is to keep the thin walled AR bolts from breaking lugs. Same as the Grendel, or 7.62x39.

 

[CJ6]

Yes, I get that...It just makes it weird that the 5.56 NATO round is at 60 kpsi and the new 6.5 ARC is not.

 

[gunsandgunsmithing]

Yes, I get that...It just makes it weird that the 5.56 NATO round is at 60 kpsi and the new 6.5 ARC is not.

The difference is because of additional bolt thrust/stress due to a larger diameter case head. A larger case head simply generates more thrust at the same pressure. That's why the loads are reduced vs 5.56. It's not about the thinner bolt head either. The math works out pretty much spot on, based on the difference in pressure and the difference in case head diameter. Not saying that the thinner bolt head is or isn't weakened but it's not the reason for the reduced pressure. The max loads are based on bolt thrust and the AR15 limitations to handle that thrust with standard bolts. By my math, a ARC case@52KPSI generates 4447 sq inches of bolt thrust and a 5.56 @62KPSI generates 4382. So 4,400 lbs/sq in nominally for both cartridges at those respective pressures, 52K vs 62K. The bolt lugs are the weak link in the ar15 and the max pressures were adjusted based on bolt thrust.
Here's a good read along with how to calculate bolt thrust, about half way down the page.

A Look at Bolt Lug Strength - Lilja

All action designers are concerned primarily with producing a safe and functional product. All other considerations such as weight, finish, eye appeal and other cosmetics are secondary. From a safety standpoint, the strength of the bolt lugs is of prime concern. Bolt lug shear strength depends...

riflebarrels.com

 

[6bra1k]

The difference is because of additional bolt thrust/stress due to a larger diameter case head. A larger case head simply generates more thrust at the same pressure. That's why the loads are reduced vs 5.56. It's not about the thinner bolt head either. The math works out pretty much spot on, based on the difference in pressure and the difference in case head diameter. Not saying that the thinner bolt head is or isn't weakened but it's not the reason for the reduced pressure. The max loads are based on bolt thrust and the AR15 limitations to handle that thrust with standard bolts. By my math, a ARC case@52KPSI generates 4447 sq inches of bolt thrust and a 5.56 @62KPSI generates 4382. So 4,400 lbs/sq in nominally for both cartridges at those respective pressures, 52K vs 62K. The bolt lugs are the weak link in the ar15 and the max pressures were adjusted based on bolt thrust.
Here's a good read along with how to calculate bolt thrust, about half way down the page.

A Look at Bolt Lug Strength - Lilja

All action designers are concerned primarily with producing a safe and functional product. All other considerations such as weight, finish, eye appeal and other cosmetics are secondary. From a safety standpoint, the strength of the bolt lugs is of prime concern. Bolt lug shear strength depends...

riflebarrels.com

serious question..if they used a rebated case with a smaller face, they could safely go to higher pressure ??

 

[Laurie]

Yes, I get that...It just makes it weird that the 5.56 NATO round is at 60 kpsi and the new 6.5 ARC is not.

Another couple of looks at this issue supporting @gunsandgunsmithing 's answer:

https://www.thereloadersnetwork.com/2018/12/29/ar-15-reloading-do-not-let-this-happen-to-you/

https://www.whiteoakarmament.com/blog/hornady-s-new-6mm-arc.html

As to why SAAMI adopted the lower (AR) pressure ceiling rather than the higher (bolt-gun), that would be normal as experience has shown many times over the decades that where two pressure levels co-exist with factory ammo or handloading, there are always people who either can't understand the warnings about use in weaker firearms or think 'It doesn't apply to me'. 44-40WCF and 45 Colt are two well known examples of where you could once buy 'High performance / pressure' factory ammo that was eventually discontinued on safety grounds. The thinking may also have been that this cartridge will predominately see use in AR type rifles.

Whilst the 5.56 v Grendel / ARC pressure difference makes sense to me, what I've never understood is why 223 Rem has a 55,000 psi SAAMI ceiling, Nato and the European CIP 62,000 psi for the same cartridge in the same firearms. (Yes, I know that different points of the case are used for pressure testing between the two standards, but does it affect results by this amount?)

 

[David Milisock]

do not know where you are looking but in the middle of this massive run/shortage i bought 200 pcs of lapua 220 russian no problem.
as far as the ar,i see no future other than "its new , i want to try it". its death kneal to me was the 50kpsi number for max.

The 6MM ARC has been adopted by special forces, as far as I've heard the SEALS are using it to some degree.

The original 5.56, M193 was 52,000 PSI and 20" barrels. As the M4 with shorter barrels became the norm the M855 was designed and then the M855A1 with a pressure of 62,285 PSI ( I believe), with a result of decreased barrel life compared to the original M193.

The 6MM ARC in a 20" barrel, outperforms the 308, 6.5 Grendal and the 6.8SPC for long range as well as CQB operating at 52,000 PSI for AR15 platforms. It also adapts well to shorter barrel lengths such as used in traditional M4 rifles. This reduces wear on the barrel allowing burst and rapid single fire while maintaining long range accuracy. My Aero Precision shoots 1/2" groups at 100 yards.

In bolt rifles with traditional 62,000+PSI pressures in 20 in barrels comes close to 243 Winchester capabilities.

I bought 500 rounds of factory ammo just for the brass. It was only twenty cents more than new brass alone.

 

[JEFFPPC]

A Tika Varmint or 12 Savage would be nice.

 

[6bra1k]

.

The 6MM ARC in a 20" barrel, outperforms the 308, 6.5 Grendal and the 6.8SPC for long range as well as CQB operating at 52,000 PSI for AR15 platforms.

can you show me some DATA to support the claim ??
thanks