6mm ARC availability

[Gtscotty]

Based on experience, I lean toward @243Mendoza and his position regarding pressures. I'm not going to doubt you either but I do think you are very near where fatigue may show up as broken bolt lugs,, eventually.
I hope not but based on pressures and my experience with different Grendel versions in both bolt guns and in ar's, you are operating at fringe pressure levels for a reliable ar15 platform rifle, at your stated velocities. It might hold up for a while and it might hold up forever but I'm only stating my experience, not absolutes.
You are clearly a fan of the cartridge and I don't fault or credit that but you do take promoting it pretty serious, for whatever reason. It might be the best thing since sliced bread but is virtually a twin to both a 6ppc and a 6 Grendel, with no significant advantages over either. So, I don't see the big deal. Now, when Lapua starts making good brass for it, it might have something going for it. That being an already formed case that can emulate a ppc or 6 Grendel with less work. Until then, the only thing it has over those is factory ammo, a platform that can't stand up to its ideal pressures and very low quality brass options. Saami approval might open doors to fix both but I think makers are reluctant to publish bolt and gas gun data. I don't think anyone has said it's a bad round. He'll, it can't be. It falls right between and very close to two very good cartridges. Brass and bolts hold it back, for now, imo.
Otherwise, it's been done and has already been proven to be an excellent cartridge.
There are better bolts for ar15s that help but I've not seen one that will hold up to modest ppc br loads yet, over the long haul.
One more thing that irks me a little is how Hornady promotes speeds without clearly stating bbl lengths.
Fwiw.

I did my PE in materials and machine design, so I have a familiarity with how fatigue mechanics works. From my experience, to estimate the fatigue life on my bolt with my loads, you'd have to know some information about both that I don't think you know.

What experience exactly are you basing your assessments on. Experience with 6mm ARC using similar loads or factory ammo? If so, what bolt type/material and what fatigue life did to see at what pressures? It sounds like both you and 243Mendoza are speculating, maybe based on the bad old days of 6.5 Grendel when lots of folks were shooting loads that were over the 52ksi limit, or maybe based on the various Grendel wildcats that are generally lacking in real pressure tested data.

I like the ARC, but I'm not a fan of it more than say the 6GT, 6.5 Creedbro, .30-06, or .223, for their own niches. I like cartridges that just work well for their intended purpose with minimal messing around. I do think it's about as good as you can do for long range in an AR-15, but mostly I hate to see threads like this get clogged up with bad information, speculation in place of data, and nonsense about stolen ideas.

I think your last statement about Hornady not specifying barrel length for speeds is pretty baseless. Every bit of Hornady 6mm ARC data I've seen clearly states the barrel length (see attached). Beyond that they put out a table that shows the speeds to expect for various loads across various barrel lengths.... I really don't know what else they could do to satisfy you in that regard?

 

[Raptor]

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.

Like was stated earlier "It is the thin bolt head" .223 has a much thicker bolt head and can take enough pressure to blow up a case and not hurt the bolt. NOT SO with the ARC bolt... If you're building a bolt gun it will do anything a 6PPC will. It is nearly an identical twin to it......

 

[243Mendoza]

I ran the Hornady specks in my calculator. For my rifle I ran my clocked speeds and measured drops in my 16" barrel and they closely matched Hornady velocities at the muzzle and the calculated drops were very close to my measured dropsvand Hornadys table.

According to Quickload, the max load with Lvr is 29.2gr using the 108ELD-M giving a velocity of 2439fps in a 16" barrel.
The Hornady loadsheets gives a max load with Lvr of 29.7 resulting in a velocity of 2505 in a 16" barrel.

Not sure how you got another 250fps out of your rifle with the same powder and at max pressure of 52ksi.

 

[243Mendoza]

...

What experience exactly are you basing your assessments on. Experience with 6mm ARC using similar loads or factory ammo? If so, what bolt type/material and what fatigue life did to see at what pressures? It sounds like both you and 243Mendoza are speculating, maybe based on the bad old days of 6.5 Grendel when lots of folks were shooting loads that were over the 52ksi limit, or maybe based on the various Grendel wildcats that are generally lacking in real pressure tested data.
...

Yes I am basing my experience on my rifle with the 243LBC AR 40deg chamber and my friend's rifle with the 6Fat Rat chamber. We based our loads on Whitley's loads which we found to be way over pressure for those cartridges. It looks as if the 6ARC specs are more in line with safe loads.

 

[gunsandgunsmithing]

I did my PE in materials and machine design, so I have a familiarity with how fatigue mechanics works. From my experience, to estimate the fatigue life on my bolt with my loads, you'd have to know some information about both that I don't think you know.

What experience exactly are you basing your assessments on. Experience with 6mm ARC using similar loads or factory ammo? If so, what bolt type/material and what fatigue life did to see at what pressures? It sounds like both you and 243Mendoza are speculating, maybe based on the bad old days of 6.5 Grendel when lots of folks were shooting loads that were over the 52ksi limit, or maybe based on the various Grendel wildcats that are generally lacking in real pressure tested data.

I like the ARC, but I'm not a fan of it more than say the 6GT, 6.5 Creedbro, .30-06, or .223, for their own niches. I like cartridges that just work well for their intended purpose with minimal messing around. I do think it's about as good as you can do for long range in an AR-15, but mostly I hate to see threads like this get clogged up with bad information, speculation in place of data, and nonsense about stolen ideas.

I think your last statement about Hornady not specifying barrel length for speeds is pretty baseless. Every bit of Hornady 6mm ARC data I've seen clearly states the barrel length (see attached). Beyond that they put out a table that shows the speeds to expect for various loads across various barrel lengths.... I really don't know what else they could do to satisfy you in that regard?

You really need to get that thorn out. It's making you grouchy. I didn't attack you, yet you are attacking me. I simply stated my experience and I no longer feel any need to justify my statements to you beyond what I did. If you don't believe it...it's still sort of a free country. Seldom do I see someone take such offense to something so impersonal. Go enjoy your 6 arc until the cows come home. Bye!

 

[David Milisock]

According to Quickload, the max load with Lvr is 29.2gr using the 108ELD-M giving a velocity of 2439fps in a 16" barrel.
The Hornady loadsheets gives a max load with Lvr of 29.7 resulting in a velocity of 2505 in a 16" barrel.

Not sure how you got another 250fps out of your rifle with the same powder and at max pressure of 52ksi.

I only got 2625, and then who knows maybe my chronograph is off maybe different lot of powder. I didn't exceed what ever powder charge is printed in their recipe.

Anyone who exceeds the formula in their gas gun is looking for trouble.

The interesting thing is Hornady printed velocities by barrel length starting at 24" down to 14" and it turned out to be fairly accurate for me as are their bullet drop tables.

Even as a bolt cartridge it's not bad, it fits micro actions and at 62,000 PSI is a just step behind maxc243 loads.

 

[SD guy]

I for one am very pleased to see Hornady took the 6mm Arc & standardized it in SAMI fashion. I see little & more like no down side to the .03" shorter head space than some of the non standardized 6mm Grendel wildcats. The shorter shoulder location really makes sense for long boolets in Mini action Bolt action rifles & AR rifles.

What Hornady has done with both Bolt gun & gas gun load data is admerable IMHO.

For those who have hurt feelings regarding Hornady not giving credit to one of the preceding similar wildcats, Suppose there is no reason short of initiative & financial clout, the wildcat couldn't be put together with SAMI specs as well.

Very happy with my 6mm ARC bolt action rifles thus far. My CZ 527 being my current favorite. Fairly sure I would not be any happier with a 6mm Grendel chamber in the CZ527 action for 108 grain bullets for example..

 

[CAPTHOOK58]

Love this cartridge. Removed the barrel from my .308 hog hunter and attached a McGowan 24" Vamint Contour barrel. Got .2 MOA on both 103 Bison Ballistic Claymore and Hornady 108ELDM bullets @100yds. Leverevolution is the powder on both.

 

[rickt300]

Love this cartridge. Removed the barrel from my .308 hog hunter and attached a McGowan 24" Vamint Contour barrel. Got .2 MOA on both 103 Bison Ballistic Claymore and Hornady 108ELDM bullets @100yds. Leverevolution is the powder on both.

Aren't the case head diameters different enough to create extraction issues? .441 to .473

 

[CJ6]

There are actions/bolts that will pull both sized cases.

 

[CAPTHOOK58]

Aren't the case head diameters different enough to create extraction issues? .441 to .473

I changed out the bolt head.

 

[rickt300]

I changed out the bolt head.

Who makes the bolt head you used? It would be nice to have a working mag box too. Seems like you could alter the feed lips of your 308 mag box. block the mag box and shorten your follower. Some artful spring work and your set.

 

[CAPTHOOK58]

Sorry for the delay but I used a grendel bolthead. Believe I got it from Midway but they out of stock now. The PPC uses the same. Pacific Tool and Guage may be making most or all of them.