Hornady's 6mm ARC. Who's all in?

[Tokarev]

I think it was SLG who originally brought up 6.5 Grendel on PF. He was pretty clear in describing it as a hobby gun for hunting and nothing serious use. I think that's a good description and realistic expectation of Grendel and the ARC. Hobby cartridges for long range and or hunting.

Except the ARC was apparently developed at the request of the US Army. It could have been developed for AMU but it sounds like it was spec'ed out for an SF unit. It will be interesting to see if military use easily translates into civilian use as was the case with 308 and 223.

I helped out with an LVPO course last fall up in Phoenix. We were talking scopes and calibers. One of the officers in attendance said his SWAT team had recently attended training with one of the SF units. I forget now which one he said. Anyway, this unit was apparently using 11.5" uppers alongside 18" in 6 ARC and was reporting good terminal effects from both lengths.

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[Borderland]

Like any real wildcatter, I'm going to wait to see which one survives. In 5-10 years, I'll become fascinated by the ones that didn't and scrounge dies and form brass, while lecturing on why you all chose poorly.

In a thousand years an excavation in the US won't reveal any widespread use of 6mm cartridges. They will be like fish bones in the Norse villages of Greenland.

[OlongJohnson]

The Department of Defense must have needed some 6ARC for their hobby of shooting bad guys in the face when they adopted it.

6ARC should have less bolt thrust than 6.5G, which was the issue early on with the Grendel.

Am I wrong that bolt thrust = pressure * case head area (approximately)? 6ARC and 6.5G would be the same at the same pressure.

I am in the Grendel crowd. I think target shooters are going to prefer the ARC for long range shooting; ARC ballistics are better than the Grendel. However, it's hard to beat the Grendel for pigs and predator hunting. I do not speak from any experience with the ARC. I hear of some Grendel shooters who have had some fun shooting the ARC, but they prefer the Grendel for pigs. The extra bullet weight of the Grendel is preferred.

The 6.8 guys will argue about pigs and predator hunting. The 90gr TTSX was designed to optimize the cartridge, and a rifle-length barrel sends it ~2900 fps. And there's Bill Wilson with his .300 HAM'R...

[littlejerry]

Am I wrong that bolt thrust = pressure * case head area (approximately)? 6ARC and 6.5G would be the same at the same pressure.



The 6.8 guys will argue about pigs and predator hunting. The 90gr TTSX was designed to optimize the cartridge, and a rifle-length barrel sends it ~2900 fps. And there's Bill Wilson with his .300 HAM'R...

You are correct about bolt thrust. Although one key component in AR bolt life is chamber pressure during bolt unlocking. I have no idea how 6.5G, 6ARC, and 5.56 compare. This is also build dependent with gas port size, location, and barrel length determining the timing/pressure.

On paper the 6.8 and 6.5 are so close it doesn't matter out to ~200-300 yards. The key advantage of 6.5 and more so the 6ARC are high BC projectiles which provide both the improved teminal performance of many wildcats but also improved LR hit probability over 5.56.

[Shotgun]

I think it was SLG who originally brought up 6.5 Grendel on PF. He was pretty clear in describing it as a hobby gun for hunting and nothing serious use. I think that's a good description and realistic expectation of Grendel and the ARC. Hobby cartridges for long range and or hunting.

That is exactly why I have a Grendel. I wanted something better than 5.56 for pigs primarily but also something that I could shoot long range for fun. I will never be a long range competitor, but it is fun to shoot some long range steel from time to time. The Grendel is perfect for that. Some of the ARC guys may take issue with their new cartridge of the day not being a serious long range shooter.

You are correct about bolt thrust. Although one key component in AR bolt life is chamber pressure during bolt unlocking. I have no idea how 6.5G, 6ARC, and 5.56 compare. This is also build dependent with gas port size, location, and barrel length determining the timing/pressure.

On paper the 6.8 and 6.5 are so close it doesn't matter out to ~200-300 yards. The key advantage of 6.5 and more so the 6ARC are high BC projectiles which provide both the improved terminal performance of many wildcats but also improved LR hit probability over 5.56.

Some are bringing up a bolt face issue, but reliability is of small concern in a hobby rifle. Yes, I want the rifle to run, but the only risk I run is a spoiled hunt. Besides, and mine hasn't reproduced yet, I am learning that Grendels (and perhaps ARCs) tend to breed like rabbits. So, there would likely be another rifle along for a hunt, even if only 5.56 before another Grendel shows up in the gun cabinet. Absent the zombie apocalypse and running out of other options, I would not be using my Grendel for defense.

[Hambo]

But you'll be running them with a 10-inch Contender barrel, so they'll all underperform and put a flash-bang in your face anyway.

#30HerrettMasterRace

[OfficeCat]

6mm ARC vs 6.5 Grendel feels a lot like 270 vs 30/06 circa the 1920s. Neck the case down a little for a little more velocity and a little flatter trajectory with bullets os similar sectional density. Both sides will have their proponents but the differences will probably be more pronounced on paper and in the mind than in the field.

That said I'm a Grendel fan and will stick with it. Everything's a compromise and the Grendel is the best I've found to meet my personal and arbitrary specifications. It delivers the minimum bullet weight, diameter, sectional density I'm comfortable with in a sufficiently light and handy package to carry into the woods for use on deer primarily within 100 yards but with the ability to reach out 200-250 yards should thay occasion arise, although in nearly 40 years of hunting it hasn't yet. The ability to break through bone and reliably penetrate are prioritized over velocity and explosive tissue disruption as mimimal meat damage is also specified.

The Grendel with a traditional 120 grain spitzer at around 2450 fps is kind of the sweet spot for me and has thus far performed to spec on the two biggest whitetails I've ever shot. All these specificatitions of mine are based on my own highly subjective values and opinions and may not correspond to anyone else's experiences but I'm pretty satisfied with the Grendel.

[Flamingo]

I am in the process of building a 6 ARC or 6.5 Grendel. I bought some magazines, a BCG, an upper receiver, and a lower. I think the deal breaker for me will be finding a good barrel for a decent price. I also will need a decent LPVO for it.

[alamo5000]

I just finished out my 6ARC upper. Well, almost. I am sorting out some issues related to the optic (IE I need to buy a new one now).

I am on board. I think this will add a whole new dimension into the AR capabilities. Basically doubling the range (or more) is a big deal. Also I don't know if you've seen them but check out some SBR numbers. A 12.5" will be a banger.

[Skinner Precision, LLC]

Am I wrong that bolt thrust = pressure * case head area (approximately)? 6ARC and 6.5G would be the same at the same pressure.



The 6.8 guys will argue about pigs and predator hunting. The 90gr TTSX was designed to optimize the cartridge, and a rifle-length barrel sends it ~2900 fps. And there's Bill Wilson with his .300 HAM'R...

You are not wrong the regards to total bolt thrust-it will be very similar for the ARC and Grendel as long as the PSI is the same, the Time vs Pressure curve may be slightly different but not something that an individual should/would worry about IMO.
As someone who has both 6mmARC and 6.5 grendel reamers in inventory, and has seen and used "PPC bolthead" 6.X mm wildcat AR's in play and competition for quite a while- the allure is strong in regards to the performance vs other options in the AR 15 platform but it comes at a cost in regards to the service life of bolt heads and the reliability of the associated magazines. Much like a 1911/2011 may be the perfect answer for the individual, the technical problems associated with large numbers of them makes more widespread agency issue more "Problematic" without cubic support dollars. YMMV