Hornady 6mm ARC "New" cartridge

[ormandj]

In the case size, AR comp should be about the perfect powder. H4895 also.

There's load data for H4895, and it's not great re: velocity. RL-15 is a little faster. Both are down > 150 fps in a 18" barrel to keep the pressure at 52kpsi vs. LeverEvolution. That's why I'm curious about AR-Comp, since I happen to have a good bit sitting around.

It's somewhere between Varget and RL-15 in burn-rate, but I don't know what the pressure curves look like in this case. I'm not trying to utmost velocity, I definitely am aiming for accuracy. This is why I don't like the temperature sensitive powders, I've been having a rough time with them with a > 30F temperature swing during the day. At the same time, I'd like to stay out of the transsonic zone from an 18" barrel at 1000yds, and prefer to avoid going over 52kpsi in doing so.

 

[Hohn]

I’d take cues from 6ppc loads for heavier bullets, given the similarities.

8208 is a favorite if mine but not really temp stable. Might work well in that case though if you can get speed at a node that’s wide.

 

[Gtscotty]

I’d take cues from 6ppc loads for heavier bullets, given the similarities.

8208 is a favorite if mine but not really temp stable. Might work well in that case though if you can get speed at a node that’s wide.

While not part of the extreme line 8208 is supposed to be reasonably temp in-sensitive, certainly better than double-base ball powders. Have you had problems with 8208 in varying temperatures?

I haven't seen any big issues with 8208 in different temperatures, but I mostly use it in ARs, as long as things still line up out to the 700yd berm like they're supposed to I might not notice.

 

[SG4247]

I really like 8208 in the 6mmAR.

Won a pile of trophies shooting 8208 with the 95 gr SMK out to 500m in a 22” AR.

Used it in the 6.5 Grendel also, with good results. It did pop a primer on a couple of match days where the temp was over 100F.

 

[Hohn]

While not part of the extreme line 8208 is supposed to be reasonably temp in-sensitive, certainly better than double-base ball powders. Have you had problems with 8208 in varying temperatures?

I haven't seen any big issues with 8208 in different temperatures, but I mostly use it in ARs, as long as things still line up out to the 700yd berm like they're supposed to I might not notice.

I've personally had no issues with 8208 but then I don't own a chrono and only judge based on the target. I'm saying it's temp-sensitive only based on test data I've seen showing it to be notably more so than powders like, say AR Comp.

I love 8208 though. Super clean, super accurate. Can't ask for much better. It's a warm load but 23.6gr under an 80 ELD has been very solid in my AR. Cleaned at 600 with that load and had lots of 198 and 199s with it.

 

[Gtscotty]

Sorry if this has been posted here already, but Hornady recently posted up some more load data, both for gas gun and bolt gun pressure levels.

https://www.hornady.com/assets/site/hornady/files/load-data/6mm-arc-gas-58-105gr-data.pdf

https://www.hornady.com/assets/site/hornady/files/load-data/6mm-ARC-gas-108-110gr-data.pdf

https://www.hornady.com/assets/site/hornady/files/load-data/6mm-arc-bolt.pdf

 

[Kracken McGraw]

Ok I’ll ask the question, what actions are going to be used for the arc? Excuse me if this had already been covered. I see that a Howa mini action has been used, will a Remington or clone work or be modified to work?

 

[ormandj]

Ok I’ll ask the question, what actions are going to be used for the arc? Excuse me if this had already been covered. I see that a Howa mini action has been used, will a Remington or clone work or be modified to work?

You can use just about any action you like as long as you can get the right bolt face, but the mini actions are a great fit and cut down on length and weight. Howa mini and CZ 527 are the top two in this regard. 6.5G variants will have the correct bolt face.

 

[Kracken McGraw]

You can use just about any action you like as long as you can get the right bolt face, but the mini actions are a great fit and cut down on length and weight. Howa mini and CZ 527 are the top two in this regard. 6.5G variants will have the correct bolt face.

Thanks, it would sure be nice to get a action to fit it that would work with all the aftermarket 700 stocks.

 

[Hohn]

Saw a JRB video where he launched into 6 ARC in an 18" Odinworks AR barrel. Factory ammo shooting 105 BTHPs is coming in around 2430 fps. If you compare that to a Grendel in an 18" gun, the Grendel wins pretty handily.

I sure hope they 6 ARC can get closer to 2650 with 105s and 2600 with 108s. Otherwise, there's no reason to choose it over a Grendel. The grendel has a bit more case capacity, Lapua brass, and is better for hunting.

I think the ARC vs Grendel testing is really going to come down to barrel length and how warm you load. The Grendel does have a 15 year headstart in development, but not really because the 6 ARC being so close to cartridges that already have a substantial experience base (ahem, 6mm AR), I suspect the ARC doesn't have a huge amount of untapped potential.

 

[ormandj]

Saw a JRB video where he launched into 6 ARC in an 18" Odinworks AR barrel. Factory ammo shooting 105 BTHPs is coming in around 2430 fps. If you compare that to a Grendel in an 18" gun, the Grendel wins pretty handily.

I sure hope they 6 ARC can get closer to 2650 with 105s and 2600 with 108s. Otherwise, there's no reason to choose it over a Grendel. The grendel has a bit more case capacity, Lapua brass, and is better for hunting.

I think the ARC vs Grendel testing is really going to come down to barrel length and how warm you load. The Grendel does have a 15 year headstart in development, but not really because the 6 ARC being so close to cartridges that already have a substantial experience base (ahem, 6mm AR), I suspect the ARC doesn't have a huge amount of untapped potential.

Something is off with his barrel or perhaps ammo. 108s at 2575fps are max book loads for gas gun (52kpsi) / low pressures in an 18” barrel. https://www.hornady.com/assets/site/hornady/files/load-data/6mm-ARC-gas-108-110gr-data.pdf

If comparing to Grendel in a gas gun, make sure to restrict it to 52kpsi, too.

Here is bolt gun data, which can obviously be loaded to higher pressures: https://www.hornady.com/assets/site/hornady/files/load-data/6mm-arc-bolt.pdf

 

[RickB]

It’s not just the JSOC had the flexibility to procure things on an expedited basis; it’s that Big Army acquisitions are so political and broken that it’s a miracle when they get anything done.

Id really like to see the 6ARC in a bolt gun that takes AR mags. The additional performance at higher pressures should get you a legitimate 2800 or so with a 108 in a 20” barrel. And in a super light < 6# gun you have mild recoil and remarkable capability.

Something like a Ruger American Predator in 6 ARC with up to 20+ rounds in a mag? Sounds like the perfect walking/offhand rifle to me. Give it a lightweight 4x or 6x AR scope and it would be awesome.

If using a bolt gun, what you are describing is similar to some PRS rifles, although they are not making use of AR magazines.

The problem with what you describe is bumping pressures up. That is a prescription for disaster if you have an AR and fire the overpressure in it by mistake. There also would be no factory ammo at the higher pressure loading. One of the benefits of the round is the availability of factory ammo.

But, to return to the scout rifle concept, utilizing AR mags, it would be an attractive concept in 6 ARC or 6.5 Grendel.

 

[RickB]

Saw a JRB video where he launched into 6 ARC in an 18" Odinworks AR barrel. Factory ammo shooting 105 BTHPs is coming in around 2430 fps. If you compare that to a Grendel in an 18" gun, the Grendel wins pretty handily.

I sure hope they 6 ARC can get closer to 2650 with 105s and 2600 with 108s. Otherwise, there's no reason to choose it over a Grendel. The grendel has a bit more case capacity, Lapua brass, and is better for hunting.

I think the ARC vs Grendel testing is really going to come down to barrel length and how warm you load. The Grendel does have a 15 year headstart in development, but not really because the 6 ARC being so close to cartridges that already have a substantial experience base (ahem, 6mm AR), I suspect the ARC doesn't have a huge amount of untapped potential.

I believe Hornady has done a much better job of development than Federal did with the .224 Valkyrie. There are multiple loads that shoot well enough at public release. Analyzing some targets posted online I will not be surprised if there is some refinement in barrel twist rate for the heavier bullets.

we should keep in mind that the “undisclosed DoD client” (SOCOM) had some very specific requirements which the 6 ARC appears to meet. Soon, perhaps, there will be information filtering out about its performance down range where it really matters.

 

[RickB]

There's load data for H4895, and it's not great re: velocity. RL-15 is a little faster. Both are down > 150 fps in a 18" barrel to keep the pressure at 52kpsi vs. LeverEvolution. That's why I'm curious about AR-Comp, since I happen to have a good bit sitting around.

It's somewhere between Varget and RL-15 in burn-rate, but I don't know what the pressure curves look like in this case. I'm not trying to utmost velocity, I definitely am aiming for accuracy. This is why I don't like the temperature sensitive powders, I've been having a rough time with them with a > 30F temperature swing during the day. At the same time, I'd like to stay out of the transsonic zone from an 18" barrel at 1000yds, and prefer to avoid going over 52kpsi in doing so.

Don’t forget that ammo manufacturers have access to powders not available to the general public.

 

[ormandj]

Don’t forget that ammo manufacturers have access to powders not available to the general public.

Not lost on me at all, I spent some time on the phone with Hornady over the last few months discussing powders for this cartridge, hah. Even their own folks wish they could buy their mixes off the shelf. FWIW the guys who didn’t care about temperature sensitivity were using CFE223 or LeverEvolution and those that did were using H4895 or XBR8208.

I asked about AR Comp and none had tried it. I keep hoping it will work out well since it’s the least temp sensitive powder I have, and I think the burn properties might be a reasonable fit. Won’t get me to leverevolution performance but I’m only looking for supersonic at 1000 from an 18” barrel in a gas gun.

 

[Gtscotty]

Saw a JRB video where he launched into 6 ARC in an 18" Odinworks AR barrel. Factory ammo shooting 105 BTHPs is coming in around 2430 fps. If you compare that to a Grendel in an 18" gun, the Grendel wins pretty handily.

I sure hope they 6 ARC can get closer to 2650 with 105s and 2600 with 108s. Otherwise, there's no reason to choose it over a Grendel. The grendel has a bit more case capacity, Lapua brass, and is better for hunting.

I think the ARC vs Grendel testing is really going to come down to barrel length and how warm you load. The Grendel does have a 15 year headstart in development, but not really because the 6 ARC being so close to cartridges that already have a substantial experience base (ahem, 6mm AR), I suspect the ARC doesn't have a huge amount of untapped potential.

Are you talking about this video?

Here's a screen shot of his velocities for factory and a few different handloads:


Factory 105gr loads with the oal shortened clocked 2,591 fps. (several folks including JRB have reported an early lot of factory 105s sticking in the lands in Proof and Odin barrels.) The data from his first outing looks pretty good for an 18" to me, he's 130 fps faster with 108gr ELDs than I am with 123gr in my 16" grendel, and isn't really leaning on the cartridge.

 

[Gtscotty]

If using a bolt gun, what you are describing is similar to some PRS rifles, although they are not making use of AR magazines.

The problem with what you describe is bumping pressures up. That is a prescription for disaster if you have an AR and fire the overpressure in it by mistake. There also would be no factory ammo at the higher pressure loading. One of the benefits of the round is the availability of factory ammo.

But, to return to the scout rifle concept, utilizing AR mags, it would be an attractive concept in 6 ARC or 6.5 Grendel.

I don't see the existence of "bolt gun only" load data as a problem at all. If someone can't keep their bolt and gas gun ammo separate and do fire some 62ksi ammo in the gas gun, they are looking at reduced bolt lug life, not Kabooms. That's how Grendel bolts got their reputation for lug failure, folks loading to stupid pressures. If you load to stupid pressures in a gas gun and set back or crack lugs, the solution is to buy a new bolt and stop loading stupid. I don't see the hypothetical situation of messing up and shooting your bolt gun only ammo in your AR as any different, new bolt if necessary and be more careful, very unlikely to be disastrous.

I would be interested to see Hornady publish some bolt gun only Grendel data to go with the ARC data.

 

[Kracken McGraw]

Not lost on me at all, I spent some time on the phone with Hornady over the last few months discussing powders for this cartridge, hah. Even their own folks wish they could buy their mixes off the shelf. FWIW the guys who didn’t care about temperature sensitivity were using CFE223 or LeverEvolution and those that did were using H4895 or XBR8208.

I asked about AR Comp and none had tried it. I keep hoping it will work out well since it’s the least temp sensitive powder I have, and I think the burn properties might be a reasonable fit. Won’t get me to leverevolution performance but I’m only looking for supersonic at 1000 from an 18” barrel in a gas gun.

Was H322 mentioned in the conversation with Hornady. I noticed it being used in the Grendel a lot and it is a Hodgdon Extreme powder to help with temp swings.

 

[ormandj]

Was H322 mentioned in the conversation with Hornady. I noticed it being used in the Grendel a lot and it is a Hodgdon Extreme powder to help with temp swings.

Nope, never came up. I'm actually surprised at some of the powders they didn't test, but I suppose they can't test them all. I just wish I had a pressure barrel so I could test these powders and see what max loads were. If someone with Quickload who has modeled the cartridge is willing to run numbers with H322 and AR-Comp +108gr ELD-M and see where 52k psi gets you with velocity, that would be nice.

 

[SF-Guy]

Unless I am reading the prints wrong, this 6ARC case is .030” shorter to the shoulder, than standard 6.5 Grendel SAAMI. So if this is correct, it is not a necked down 6.5 Grendel.

This makes no sense, since it would be alot of extra headspace if this brass is used in the “OLD STD” 6AR chamber.

This ammo would also load and probably fire in a AR chambered in a 6.5 Grendel.

The 6mmAR from Robert Whitley is actually the 6.5 Grendel necked down. That extra 0.0030” on the shoulder is a little powder capacity. Mine shoot terrifically and the 6mmARC will too, but i will stick with the 6mmAR because it is so easy to load and shoot. I am using Berger and other 105’s and 107 SMK’s with great success. My upper has just over 5100 rds and still shoots well for me, so i will wait and find out what i can get.