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New 6mm Advanced Rifle Cartridge

I have a grendel 20 inch upper need to install my agb today it is overgassed.
That has held up load development.

It's fun to shoot.

But at the price of a barrel and new set of dies I too can join the cool kids on the block.

Certainly not knocking the new round and the request of a comparison was legitimate .

I believe you are right, every caliber has that one certain bullet weight with the perfect bc.

I'm working on the 123 sst myself for hunting and after talking to the fine folks at Berger may give a couple of thiers a try.

The hybrids seem like a no brainer for me.

If I can cram enough powder in them they should be a nice option to the sst. Hope I don't over do it.
The only factory load I found with my Grendel that shot well, before I rebarreled it, was the 130 grain Berger loaded by Federal. I wasn’t super happy with the velocity, as I was barely averaging 2,300 FPS. But, I figured I might give them a go for deer. I worked for a custom rifle manufacturer that loaded Bergers almost exclusively. They always recommended a high shoulder shot to insure the bullet performed like it should. It would seem they tend to need to hit some form of bone to cause the most disruption. My new barrel likes a broader range of bullets so I will most likely use either the 123 grain SST, or the 120 grain Fusion this year. I don’t mean to come off like I’m dogging on this new cartridge. I think it will make a great addition to the line up of choices we have.
 
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I'm a huge fan of the fusions for a hunting bullet. Everything I've ever shot with them in my 308 hasn't taken more than 3 or 4 more steps. Probably 15 deer.

I muzzleload hunt mostly now.

I know the marketing is trying to get everyone to buy this arc in an AR, but I think it will really shine in a bolt gun. The cz 527 comes to mind.... I love that set trigger.
 
Hornady bullets do go splat nice once you hit something.
6EE58888-E3C5-4FFF-B5D4-30B87415C866.jpeg

Yes they do...Hornady Black 123 grain ELD Match. Vaporized the lungs and the buck didn’t make it 30 yards.
 
Yes they do...Hornady Black 123 grain ELD Match. Vaporized the lungs and the buck didn’t make it 30 yards.

Booyah. The 123gr Grendel’s effect on game is why I have two bolt guns in it now. Wonder how the 100+gr 6mms will compare; I’ve never used that bore size, let alone those specific bullet weights in that diameter, on an animal. Will be hard to top the 123gr 6.5s though.

Regardless of energy and drop figures at well-past-hunting distances, I won’t declare the Grendel dead or even obsolete until I see a lot of real world performance from the 6ARC that matches or eclipses that kind of effect on game.
 
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Got out today with the Ballistic Advantage barrel from Brownells in 20”. I dropped it into a Larue built 6.5 Grendel and put a new Monster Grendel bolt in. Low profile standard gas block and no break. Shot four groups getting it zeroed with Hornady Black all of which were about 1”. Kicking myself, I left the Magneto speed on the bench.

Went to the steel range to stretch it out. I plugged 2750 into TRASOL and found at 420, 566, and 720 that impacts were a bit high. Trued it to 2720 and it was ringing steel at 840, 950, and 1090. All of the steel is roughly full sized IPSC. Wind was 16 mph from 120 degrees, it handled the wind well.

Ran 50 rounds through it and the groups seemed to tighten up some. Last 5 rounds were at 420 and well under 1 MOA. I didn’t bother driving out to measure. I will take the chrono later this week and confirm.
 
Got out today with the Ballistic Advantage barrel from Brownells in 20”. I dropped it into a Larue built 6.5 Grendel and put a new Monster Grendel bolt in. Low profile standard gas block and no break. Shot four groups getting it zeroed with Hornady Black all of which were about 1”. Kicking myself, I left the Magneto speed on the bench.

Went to the steel range to stretch it out. I plugged 2750 into TRASOL and found at 420, 566, and 720 that impacts were a bit high. Trued it to 2720 and it was ringing steel at 840, 950, and 1090. All of the steel is roughly full sized IPSC. Wind was 16 mph from 120 degrees, it handled the wind well.

Ran 50 rounds through it and the groups seemed to tighten up some. Last 5 rounds were at 420 and well under 1 MOA. I didn’t bother driving out to measure. I will take the chrono later this week and confirm.

...............so...how much do you prefer it to 6.5 Grendel? Worth the swap, or is it just for the fun of tinkering?

Love my BA barrels, unbeatable for the price.
 
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Booyah. The 123gr Grendel’s effect on game is why I have two bolt guns in it now. Wonder how the 100+gr 6mms will compare; I’ve never used that bore size, let alone those specific bullet weights in that diameter, on an animal. Will be hard to top the 123gr 6.5s though.

Regardless of energy and drop figures at well-past-hunting distances, I won’t declare the Grendel dead or even obsolete until I see a lot of real world performance from the 6ARC that matches or eclipses that kind of effect on game.
The Grendel is really good at putting the smack down on stuff. With Hornady’s release of the 103 grain ELD-X scheduled for the Fall, I’m sure we will be seeing some ARC’s out in the wild as well.
 
...............so...how much do you prefer it to 6.5 Grendel? Worth the swap, or is it just for the fun of tinkering?

Love my BA barrels, unbeatable for the price.

For ringing steel it is flatter, less wind impact, less recoil, and could still see impacts at 1090. I like it and will leave it in. In all fairness, that doesn’t leave me without a Grendel. For hunting anything white tail or smaller I might still go with the ARC. Need some more time and load development.
 
Well, my 18” Ballistic Advantage barrel showed up today. Anyone know of a place that has ammo in stock?
Have you had a chance to shoot your barrel yet? I ordered the same one the other day, it'll be awhile before it shows up. Wondering how the gas system runs? Do you feel it's overgassed? I was torn between the 18" and 20" at rifle length gas system, but went w/ the 18".
 
Have you had a chance to shoot your barrel yet? I ordered the same one the other day, it'll be awhile before it shows up. Wondering how the gas system runs? Do you feel it's overgassed? I was torn between the 18" and 20" at rifle length gas system, but went w/ the 18".

Haven’t shot it yet but will be running an adjustable gas block. Assembled it on an Aero Precision M4E1 and had to thermal fit it. Nice and tight.
 
I'm having a few barrels spun up for 6mm ARC. What are people using for gas system length and port sizes for SBRs (10-10.5", 11.5") and 18" barrels?
 
Sure, although I haven't used the 87 Vmax; I'm mostly using heavy bullets, with some 70gr TNT for blasting just because I have a bunch.

Keep in mind all of the Lever data you'll find at this point is wildcatter's edjucated guesses; this is what works in my rifle and may or may not in yours. Also keep in mind there can be a significant difference with different brands of brass.

105gr Hornady BTHP, 2.235" OAL
Lapua brass
CCI 450 primers
Leverevolution 31.3gr - 2853 fps 24" brl - 2764 fps 19" brl - maybe max? but good brass life in my rifles

That 105gr BTHP was tested for seating depth first, with charges ranging from 30.0gr to 31.3gr for each seating depth; 2.235" was by far the best and shot pretty well despite the varying powder charges, better than any load I tried with Varget and this bullet. For general shooting I'm using 31.0gr (2835 fps in my 24"), that gives some leeway for velocity variations at different temps.

A couple other loads:

100gr SGK, 2.154" OAL
Formed 7.62x39 brass, PMC & R-P
CCI 200 primers
Leverevolution 30.4gr - 2856 fps 24" brl - 2790 fps 19" brl
That one is my standard load for the 19" gun at this point, since it's more of a hunting or "walking varminter" setup. (I made the barrel from a 20" BHW blank, and cut it as a medium-light tapered octagon barrel just to be different; total weight is just under 8 lb ready to shoot.)

70gr Speer TNT (good cheap varmint bullet), 2.255" OAL
Formed 7.62x39 brass, PMC & R-P
CCI 200 primers
Leverevolution 35.0gr - 3517 fps 24" brl - 3409 fps 19" brl
This one is not the best choice for Lever; it's maxed out for case fill and needs to be tapped to settle the powder in the case. However it does show the versatility of Lever as a good powder for this cartridge, when compared to what other powders will do with the same bullet.


One final note on Lever as a powder choice - with almost every load, I've noticed a consistent pattern: best accuracy has been obtained by
1) finding the max charge (at the longest possible OAL), and then
2) finding the optimum seating depth.
Lever likes to be pushed to max, and you'll generally find a 0.5-0.8gr window at max where charge variations do not affect accuracy much if at all. This formula has consistently given me better accuracy than most other powders, in a wide range of cartridges that use this burn rate, such as:
- 20 Tactical
- 223 Wylde / 5.56
- 243 LBC
- 6.5 Grendel
- 358 Herrett AR (my own wildcat)
- 35 Remington
I still need to test it in 308 and 35 Whelen, and expect similar results in both.

Long post, but hope that helps.

For what cartridge are these loads?

Bolt gun or AR15?
 
Good question, and while I don't have an answer for that directly I could say that I would expect barrel life to be better so if there's a deficit on brass life the cost could be offset by the barrel longevity.

I have about a dozen firings with the 243LBC AR 40 using the Lapua Grendel brass but have quite a few loose primer pockets with most primers except Wolf.
 
SAAMI max pressure on the 6.8 is 55,000psi (5.4% increase vs. Grendel variants). Doing some quick doodling in SolidWorks, if you shorten the 6.8 case to the same length as the 6 ARC, give it a 30 degree shoulder, same body taper as 6.8 SPC (magazines), and neck it down to 6mm, it has ~10-15% less internal volume than the ARC. I don't think you're going to match the ARC's performance with the 6.8 case.

Grendel case with rebated rim fitting 6.8 bolt face :)
 
I can vouch for at least one of the 6-Grendel variants doing that, and fully believe the ARC will do the same. My 24" 243 LBC (AR15 of course) load is the 105gr BTHP @ 2853 fps with Lever, and my 19" with the same load does 2760 fps. I don't know what the pressure numbers are of course, but the brass is reloadable at least 6 times, no belted cases etc. It's pretty mild to shoot as well.

How many rounds of 105gr bullets through that barrel with that load?
 
I’ve shot Defender 107 TMKs out of my 16” Grendel, shot out to 410 and estimated velocity at 2512. Just got a magnetospeed and will confirm velocities this weekend.

I ran the numbers for a 123 ELD, 107 TMK, ARC 108 ELD, and 224V 88 ELD. Tried to use FPS of factory loads in a 18” barrel I’ve found online or in articles and got the following @ 1000
123 @ 2425 - 13.3/3.3
107 @ 2550 - 12.6/3.5
108 @ 2625 -10.3/2.7
88 @ 2600 -10.6/2.8

Why this obsession with shooting a gas gun to 1000yd? Other than service rifle competition, if you are serious to shooting to 1000yd, use a bolt gun!
 
A bit over 200 with that load and that bullet. Not nearly enough to wear out the barrel if that's what you're asking, but this cartridge should give pretty good barrel life anyway.

Not worried about barrel life since my 243LBC AR 40 has 4000rounds and needs a new barrel but it also went through 2 bolts.
 
Can Grendel brass be used to make 6ARC brass? 65 cents each is spendy for gas gun brass
 
Why this obsession with shooting a gas gun to 1000yd? Other than service rifle competition, if you are serious to shooting to 1000yd, use a bolt gun!

Because it's fun? I love stretching my favorite .223 out, and the 6mm ARC will be mo-better.
 
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Oh boy - this is tempting to do an upper. Goes against my "common caliber" stategery. Got a decent scope I could mount or I could go all out (but it'd be top heavy). But I don't have 6.8 mags so I'd have to stock up on all those too. But, it's tempting to have a 1000 yard gun in a lighter weight platform than an AR-10. VERY tempting - especially as I get older. Then again, I do want a suppressor. Suppressor or upper...hmmmm.
 
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6mm arc is not in Quickload and won’t be for some time. With the similarities to the 6mm ar, I would think that I could true the case volume to match the arc case and use that to build from. Thoughts?
 
6mm arc is not in Quickload and won’t be for some time. With the similarities to the 6mm ar, I would think that I could true the case volume to match the arc case and use that to build from. Thoughts?

That's my plan, adjust the 6mm AR case volume to match an average from fired ARC cases then do some truing based on the measured velocities. I'd think that would get you close enough.
 
When I corrected for case volume Quickload was within 20 FPS for Hodgdon LVR. Looks like there is a velocity not right at 52k also.
 
Not worried about barrel life since my 243LBC AR 40 has 4000rounds and needs a new barrel but it also went through 2 bolts.

What is this "243 LBC AR 40" you keep mentioning? 243 LBC is a cartridge; what do you mean with the "AR 40" part and why is that part of your cartridge description?
 
What is this "243 LBC AR 40" you keep mentioning? 243 LBC is a cartridge; what do you mean with the "AR 40" part and why is that part of your cartridge description?

That is the description on the reamer. I suspect the reamer was designed for AR15s for a LBC cartridge with a 40 deg shoulder. The dimensions are slightly different from a straight LBC. There also exist the 243LBC AR and 243LBC AR 40 Turbo which I suspect are slight variations of Whitley's 6mmAR family.
 
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Are there any 20 inch plus barrels out there yet other than Ballistic Advantage?

Odin Works is doing a 21” and an 18”. Barrels or uppers.

Uintah Precision is doing a 22” bolt upper. Might be the ticket for me if I want to try this cartridge: I’ve got a precision AR lower with a PRS stock and a TriggerTech Diamond in it...
 
The odin works looks like what I'm looking for. The reviews online seem positive. Anyone here have personal experience? I know not in 6mm ARC, but in any of their other barrels?
 
I run an Odin Works on my 3 Gun rifle and it has been excellent. Don't really shoot it for groups but it is plenty accurate enough and runs great. I am considering the Odin option as well. I also saw Craddock has ARC barrels (and uppers) available now. Really waiting for JP but I might get itchy!
 
I had an Odin AR barrel with close 15,000 rounds through it and still shooting 1.2” groups. Gave it to buddy for his Grandson to get into three gun.
 
I spoke with Mark over at Precision Firearms and he is spinning up barrels for the 6mm ARC as well.
 
The odin works looks like what I'm looking for. The reviews online seem positive. Anyone here have personal experience? I know not in 6mm ARC, but in any of their other barrels?

I’ve got one upper build with an Odin barrel and while I don’t prefer it over the BA offerings, it is solid. I’ve got several rifles with their adjustable gas block on them (3 I think) and I love their extended mag button and have it on most of my lowers. Great company. GTG.
 
The odin works looks like what I'm looking for. The reviews online seem positive. Anyone here have personal experience? I know not in 6mm ARC, but in any of their other barrels?

I have an Odin Works .223 Wylde DMR barrel that's been a pretty solid shooter, although not outstanding. The biggest problem I had with it was that there was no undercut where the threads meet the shoulder, just a taper out from the major diameter. Two different brands of suppressor mounts wouldn't tighten all the way down to the shoulder. A local friend with a lathe fixed it, but if not for him I would have had to send it back to get fixed.

I've been much more impressed with my lightweight Wilson Combat Grendel barrel. It shoots better and more consistently than a barrel that light has any right to, plus it came from the factory with a proper undercut.

I'm waiting to see what WC comes out with, or I might just go with the longer Proof. I do wonder if Criterion is going to start making ARC barrels, they weren't on Hornady's original participating gun manufacturers list.
 
That's my plan, adjust the 6mm AR case volume to match an average from fired ARC cases then do some truing based on the measured velocities. I'd think that would get you close enough.

Ultimate Reloader did what you are thinking with QL and posted up on youtube a couple days ago.

 
6mm AR also works well as a base. Quickload and reality were only 20 FPS different. Hogdon LVR is pushing 108 ELD’s at 2,590 with a SD of 9 out of a 20” barrel. Groups were just over 1/2”.
 
Ultimate Reloader did what you are thinking with QL and posted up on youtube a couple days ago.



Yeah, I watched that, I used 6mm AR as the base and subtracted like 1.5gr to play with some numbers. Unless I missed something, UR is loading way over pressure to hit velocities though, an estimated 61 ksi in QL. He had some verbiage that flashed up on the screen saying that QL predicts peak pressure and SAAMI specifies Maximum Average Pressure MAP, insinuating that the values measured are different. As far as I know, the "Average" in MAP is the average over some sample size, or a batch, not some kind of average of a single curve.

Given that he's hitting velocities similar to his 61 ksi QL prediction, I think it's reasonable to guess that he's way over pressure. Also I read on the forums somewhere that 25.5gr H4895 in a pressure barrel gave 51.9 ksi, UR is loading 26.6gr, another indication that he's probably way over pressure.
 
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I can appreciate his effort though. He is rodding it a bit but at least he is transparent about it. My main interest is mostly due to the fact that there is finally a chambering that will fit in a Howa mini that is a little better than all the other factory options for my application.