6mm ARC

[ormandj]

Figured I'd start a thread for this cartridge. I'm in the process of collecting components, but have some introductory information.

Right now, Hornady brass is the only available factory option. It uses a small rifle primer. Dies are also Hornady only at this point, but I've reached out to Forster and L.E. Wilson and both are planning to offer options. I've also contacted AMP (annealing company) and once I have some fired brass they'll create a profile for it. Finally, I spoke to Doug Giraud and he will have an offering, as well - he's just waiting on a brass order to verify.

H4895 and IMR XBR 8208 are both supposed to be good powder options from what I've read from people who've been working with this cartridge with Hornady. I don't want to share the load data as I've not personally loaded them yet.

Please share what you've found so far if you've had a chance to work with this cartridge, the more data we have to start with, the better, since Hornady hasn't released any load data yet.

 

[rockhound78]

Why not use 6mm PPC dies and size down 6.5 grendel brass and trim. I use 6mm ppc dies to load my 243 lbc and they work fine. You wouldn't have to back off the ppc dies as much for the ARC case as I do for the LBC case.

Forum Boss: Why not just do the 6mmAR (Whitley). Just neck down Lapua 6.5 Grendel, then load and shoot.

 

[Hoser]

I am using Varget and H4895 in my 6 Grendel. Which is almost the same thing.

 

[L W P]

I'd ask Robert Whitley, since in my book he started this cartridge long before Hornady did.

6mmAR.com




6mmAR Loading Information

The target to the right represents a 20 shot MR-31 slow prone target shot prone with a sling at 100 yards using the 6mmAR. The load used was with Berger 105 gr. BT Moly bullets loaded at 2.250" OAL and 28.5 gr. H4895 powder with CCI BR-4 primers in necked down 6.5 Grendel small primer brass. In the 26" Hart barrel that shot this group, the load chronos right around 2776 fps.

6mmAR Loading Information

Chrono Results for a 600 yard load
using Berger 105 VLD's (below)

Choice of Bullets: 85 gr. to 107 gr. BTHP Match Bullets

The 6mmAR can easily be loaded with high B.C. bullets in the 85 gr. to 107 gr. range. Bullets in the 85 - 90 gr. range typically shoot well at 2800-2850 fps, and bullets in the 105-107 gr. range typically shoot well at 2700-2750 fps. Some of the bullets ideal for highpower competition are:

1. The Berger 90 gr. BT Match Bullet that has a .410 B.C. (left);
2. The Berger 105 gr. BT Match Bullet that has a .527 B.C. (second from left); and
3. The Berger 105 gr. VLD Match Bullet that has a .556 B.C. (right).

Chrono Results for a 600 yard load
using Berger 105 VLD's (below)

 

[Forum Boss]

Unless you need factory-loaded ammo, Robert Whitley's 6mmAR (and 6mmAR Turbo, and Turbo 40) is a better solution:

1. Lapua brass (superior to Hornady by far)
2. Shoulder is .030" further forward on 6mmAR for more capacity and more reliable feeding from magazine.
3. Higher quality Redding dies.
4. Whitley has 6mmAR uppers available with barrels chambered by optimized reamers.
5. If you want even more performance, go with the 6mmAR Turbo.
6. You can still use the AR bolts now being produced for the 6mmARC.

 

[Mr Underbridge]

With the shoulder being moved forward and restriction to AR magazine lengths would this cause issues with bullet going too much inside the neck?

 

[gunsandgunsmithing]

With the shoulder being moved forward and restriction to AR magazine lengths would this cause issues with bullet going too much inside the neck?

That would depend on the bullet, the freebore and seating depth. I do not believe this case is going to be at its best with the heaviest for caliber bullets...It's just a tad short on raw horsepower, IMO. That said, yes, the neck is a little shorter than say a BR and will be more critical to being set up properly for a given bullet shape and freebore, that also works well withing mag length restrictions.
I have a 6 Grendel with .070 freebore that works very well with 68 fb bullets up to 80 grain flatbases, at under 2.260 oal. If you do some research and/or measuring, the 80 gr fb Berger and the 105 have very near the same bearing surface. So, the distance from the neck shoulder junction to the lands are similar with both bullets. Of course that doesn't account for bullet tip shape and how that will affect oal vs mag length.

Bottom line, I think this cartridge will be right at home with bullets in the 90-95gr range for moderate ranges, from gas guns.

Obviously, this cartridge has garnered a lot of interest on here but I think we have to realize what it is and not try to make it into something that it's not.

Kinda reminds me of the old trck commercial where a f150 is pulling a Euclid truck. Will it do it...yes. Is it ideal for that job...no.

 

[ormandj]

People are seeing great results with the heavier bullets from all early reports. I am not interested in the 6mmAR, and the shoulder being further forward is a negative to me, that is one of the changes I appreciate most in the ARC.

Feed issues aren’t an issue with the proper magazines, it’s the same story with all the Grendel-type cartridges. I’ve got a ton of 6.5G Duramags which feed properly all day long.

Had anyone had success with StaBALL powder in the ARC or the closely related 6mmAR T40/Fatrat/etc? QL doesn’t have a profile I’ve seen yet for it. I’m just not sure if you can get enough in the case. I’m thinking it might be a little slow, but figured I’d ask since I’ve seen people run N540 with success in the 6mmAR T40.

 

[Richard Coody]

From some of it's parent cartridges it would probably work well with a slower twist barrel, shorter freebore and bullets in the 68 gr range.

Personally i like the 6mm grendel ackley improved cartridges. Best performance you are going to get out of an ar.

 

[ormandj]

Would it be possible to keep this thread to reloading the 6mm ARC and not suggestions on other cartridges to use?

 

[Hoser]

Had anyone had success with StaBALL powder in the ARC or the closely related 6mmAR T40/Fatrat/etc? QL doesn’t have a profile I’ve seen yet for it. I’m just not sure if you can get enough in the case. I’m thinking it might be a little slow, but figured I’d ask since I’ve seen people run N540 with success in the 6mmAR T40.

A local dude tried Staball in his 6BRA. Said it was waaay to slow. Guessing it will also be that way for the 6ARC.

 

[ormandj]

Oh well, was worth a shot. Something a bit slower than H4895 but temperature stable would have been nice. I can't deal with the LeverRevolution temperature swings. I've got some Varget on hand, I might try some of that, since it's not quite as slow.

 

[74Bronco]

use ppc load data, start near its top loads, just not alot of load data for over 85gr stuff, or use 6br starting data , the arc and the other grendel based 6mm's case capacity falls right in between those 2. good powders to try r15, 8208, 4895, 4034,2520,w748 cfe 223 works very well in 95-105gr loads, ramshot tac in sub 90 gr loads works too.

im running 28.5 8208 behind 95gr vld in my 243lbc ar

 

[yotehater]

It seems the new IMR-4166 would be a good powder in the burning rate with it's temperature stability and copper reducing properties.

 

[lb-ft]

I absolutely LOVE IMR-4166 in 308, but I think it's too chunky & too bulky for the 6 ARC.

If you guys haven't tried 8208XBR, it meters like a dream.

CFE223 might be good for the 6 ARC. It looks like crappy bulk salvaged powder but it is a super performer in heavy 223 for me.

 

[ormandj]

CFE223 is too temperature sensitive for me, but I bet it would work well if that's not an issue for you. 8208 XBR is a little faster than H4895, and I think we need something a little slower. IMR 4166 does look like it might slot nicely in the middle, we'll have to see how it works out.

 

[SPQR70AD]

is this new round that much better then the 6.5 Grendel? the barrels would last longer with the 6.5

 

[Laurie]

is this new round that much better then the 6.5 Grendel? the barrels would last longer with the 6.5

It's as per the 6mm Creedmoor v the original 6.5 and the balance of up and downsides for the user. 6.5 will have better barrel life - but with such a small cartridge and charge the six will still be very good. (People on the 65grendel.com forum report 9-10,000 rounds in ARs from the larger calibre, so maybe 5,000, even 6,000 from the 6mm.)

The six will have bit less recoil (but both are low-recoil irrespective) and shoot flatter - the latter a plus for unknown / estimated distance PRS type shoots and varminting. The 6.5 will have a much higher trajectory but be moved less than the six by the wind. The trajectory isn't an issue for the known distance shooter as long as the rifle sights have a suitable elevation range and the reduced windage a real plus for all target shooters, especially at longer ranges. So, if you want to shoot plates or paper at 800 yards and beyond, choose the 6.5 every time. But ... a good 105-108gn 6mm match bullet still gives creditable mid to long-range ballistics even at likely practicable MVs. (And practicable MVs from 20-inch barrel ARs may or may not be what Hornady claims. Not all are convinced - see the much more extensive thread on this cartridge on the AS Forum here:

http://forum.accurateshooter.com/threads/hornady-6mm-arc-new-cartridge.4008234/

in particular post #95 by @SG4247 and @gunsandgunsmithing (several posts but particularly #176)

Returning to pros and cons, 6.5 provides better stopping / killing power on large game, ie small to medium size deer, than an equivalent six. Even the much higher MV 243 Win engenders controversy over its big game performance - in my part of the world (the UK) the easiest way to get a long-running argument going on our deerhunting forum (The Stalking Directory, 'Stalking' from our name for the activity, deerstalking) is to raise the 243 Win's suitability for UK Deer species. Conversely, the six will offer more explosive performance with suitable bullets on varmints.

Warm little low-recoil sixes though are just FUN in any type of rifle and I'd think a helluva lot of fun in an AR-15 or equivalent semi-autos - and still provide a much more flexible offering than any 22 calibre cartridge or the 6.8SPC in the AR-15 platform. Targets, long-range, varmints, possibly deer - what's not to like?

 

[Laurie]

See also this thread:

http://forum.accurateshooter.com/threads/white-oak-armaments-thoughts-on-6mm-arc.4008640/

So, there are some serious, experienced people around with more doubts about using any 0.443" case-head dia, cartridge in the AR-15 platform than Hornady gives credit for. These doubts apply equally to the 6.5 Grendel of course since they share the same basic case. In either event, the need to restrict performance to 50-52,000 psi pressures is clear, not because of cartridge / case limitations, but to the platform.

Now, bolt-actions are another matter and one presumes that the same choice that we have for 6mm or 6.5mm Creedmoor will sooner or later be on offer from Howa, CZ, and Savage at the very least. The Cz527 and Howa 'Mini' 1500 downsized actions will be fine for the Grendel's European CIP 4,050 bar / 58.740 psi rating.

 

[SCL]

Can't find brass for the ARC. Can't even find Grendel to resize. Don't really want to go that route either. I guess I got lucky. Bought some Hornaday 103gr Black Hill. Shot 6 singles and cleaned between shots for new 24" 1/7 twist.
I reloaded those- just went off Hornady suggested load with Varget. Middle of the road 25.6 and 26- 3 each.
1st target factory, 2nd 25.6 and 3rd 26.0. All at 2.245 OAL.
100 yrds with 15+ mph wind coming from target towards me.

Guessing got lucky.