New 6mm Advanced Rifle Cartridge

[LRRPF52]

It is what the 6.5g should have been, to be honest.

Since 6.5 Grendel was targeting both the hunting crowd first, followed by the target crowd, 6.5mm was the right choice for bore diameter/projectile availability. The marketing concept focusing on hunting first was designed to establish more widespread traction since hunting rifle purchases were the main factor in people buying rifles still in the early 2000s, and are probably still that way today.

If it would have been limited to a High Power X-ring scorer and varmint cartridge, 6mm would have made more sense, but would have not realized the same marketability for those wanting to shoot larger game. At the time, it was already a stretch for a lot of Americans to even consider using anything smaller than .308 Winchester, since most were ignorant of the century of success of the 6.5x55 Mauser and early 1900s success of the 6.5x54 Mannlicher-Shoenauer.

Bill A. was also looking at doing a .257 Grendel, but there was hardly any projectile availability for the quarter bore for any target work, whereas 6.5mm had a boat load of exiting projectiles.

 

[Wnick308]

The question I have not yet seen asked or answered, but has my eyebrow raised - what’s the DoD doing with the 6ARC? Clearly not an M4 replacement, but does anyone know what group and which roles?

I want to know the same thing.

 

[LRRPF52]

Less recoil and flatter than a 6.5G. Cool.

If you shoot the same bullet weights from both, it feels the same. If you shoot heavier from the Grendel, since 108gr is about max in the 6mm AR, it will have a little more recoil.

Since both have lower chamber pressure and relatively light projectiles compared to .308, there is almost no sight disturbance on a well-balanced AR15.

6mm AR is a great little target cartridge that will kill as well. I've been wanting a 6mm AR for several years, just haven't pulled the trigger on one since I don't like fire-forming and trimming brass and I like factory ammo.

6mm ARC solves that problem for me since Hornady is releasing 3 factory loads out of the gate.

It was developed for a "notable DoD entity" to act in the DM role since enemy combatants wise up really quick to getting popped in the head by 77gr and M855A1, so they learn to stay outside of the effective range of DMs shooting 5.56 with good optics and trigger time. That ends up being around 500-600yds.

6mm Grendel-based cartridges and 6.5 Grendel easily reach past 600yds with high hit probability out to 700-1200yds, depending on the conditions, bullet used, etc.

The 107-108gr class of 6mm bullets will stay supersonic at standard atmospheric conditions even from a 16" barrel past 1000yds, with really flat trajectory and minimal wind drift.

The "notable DoD entity" also wanted something that would fit in the AR15 receiver set because the larger frame SR25 is too bulky and heavy to work with in close quarters a lot, and 7.62 NATO-based cartridges don't allow you to carry enough ammo for the same weight.

I could see a SOPMOD Block 3 Recce style carbine being one of the initial go-to set-ups, followed by the barrel getting shorter once people start seeing how well you can do with shorter barrels and high BC bullets at moderate speeds.

 

[mark5pt56]

Only if you plan to load to the lands. otherwise with .050-.100 jump all but one fit.

gotcha

 

[Mnwhiskeyman]

The amount of industry backing has me getting ready. I was super pumped to see an actual 6mm ready for the AR platform. Now I just cannot decide on barrel length. I think the time is right some of the barrel deals for pre order are a pretty good deal. I think a 24 for long range work and 18 or 16 for other applications. Very excited to get my hands on this round.

 

[slockwood]

The amount of industry backing has me getting ready. I was super pumped to see an actual 6mm ready for the AR platform. Now I just cannot decide on barrel length. I think the time is right some of the barrel deals for pre order are a pretty good deal. I think a 24 for long range work and 18 or 16 for other applications. Very excited to get my hands on this round.

It's a blast to shoot. I need to get my hands on a 24" asap to add to the data

 

[Hollywood 6mm]

I've finished my 22 BR and did a 6GT. Both work flawless.

To clarify - I was specifically referring to an AR-15. I'm well aware that the BR and GT sized cases will work in an AR-10.

 

[SuperSneakySniper]

I'm so excited to start building on this cartridge.

Quick question for anyone who might know, any ETA or guesses as to when JP might come out with their barrel offering? When I asked them yesterday they were hesitant to give out an ETA, but generally how long does it take? They would be my number one choice, but if they have a history of taking several months to come online then I might go with Proof.

 

[toygunner]

To clarify - I was specifically referring to an AR-15. I'm well aware that the BR and GT sized cases will work in an AR-10.

These are on the AR-15 platform . The upper is a 6GT and the rifle is a 22BR

 

[rjh]

I'm with CanSniper... I just bought the AR15Performance 6mmAR barrel, dies, and brass for a new AR build. This is indeed what 6.5G should have been from the start. Wonder how different the case dimensions are...

These are on the AR-15 platform . The upper is a 6GT and the rifle is a 22BR

I have been wondering about a gt in an AR for the last two months. Nice!

 

[MPrimo]

I'm so excited to start building on this cartridge.

Quick question for anyone who might know, any ETA or guesses as to when JP might come out with their barrel offering? When I asked them yesterday they were hesitant to give out an ETA, but generally how long does it take? They would be my number one choice, but if they have a history of taking several months to come online then I might go with Proof.

THIS! If JP is making barrels with matched bolts I will wait on them. Hoping for more info/timing.

 

[AccuSol-ERN]

I am still a little confused, a DoD agency is looking for a Reece/DMR type of setup and then mentions how the AR10 platform is too bulky for CQB???

Cheers to those looking for another way to "improve" a COAL limited platform.....again......and again.....and again. I know there are logistic reasons to stay with an AR15 platform...….but sooner or later you have to pay to play.

In this realm you shouldn't expect champagne on a beer budget.

Though I dig innovation and trying new stuff...….it keeps the industry going.

I look forward to seeing how this cartridge (and others) shake out in the end.

Ern

 

[Mac679]

I am still a little confused, a DoD agency is looking for a Reece/DMR type of setup and then mentions how the AR10 platform is too bulky for CQB???

In this realm you shouldn't expect champagne on a beer budget.

Um, because they developed and tested it and it fit their needs for their mission set? You're assuming that this was all decided in theory and that the end user doesn't have a champagne budget and got the year and vintage they wanted after trying out a lot of bottles.

Keep in mind over on the FB 6mm ARC page people involved in this on the manufacturing side are sharing pictures of MVs. 11.5" barrels are pushing the 108s at 2324fps. Slow, but it's still hitting with 981ft-lbs at 200yds at sea level. My last tour in Afghanistan, the valley floor was 6600' above sea level. They wanted a good all around cartridge that would work from bad breath to 500-600m. Dropping the weight by 25% from an SR25 means less fatigue, guys can move further or get on an objective faster.

 

[Ledzep]

So it’s like a 6br, did you find the capacity?

Okay got some more info, use at your own risk this is preliminary data. 103-110gr. These are Max loads, Drop 2gr or so to start.

8208xbr: 25.3gr
H4895: 25.5gr
LeverEvolution: 29.7gr (Best velocity)
AA2520: 28gr
RL-15: 27.8gr

 

[JAS-SH]

The question I have not yet seen asked or answered, but has my eyebrow raised - what’s the DoD doing with the 6ARC? Clearly not an M4 replacement, but does anyone know what group and which roles?

Hi, I wondered the same and went over to the DOD Contracts. website. I queried Barrett going back to 2018. Found two contracts. One of them was for 50 BMG rifles. I presume that the other one is more likely the one. From March 2019. Here's the information provided by DOD:

 

[Reticlelife]

Hi, I wondered the same and went over to the DOD Contracts. website. I queried Barrett going back to 2018. Found two contracts. One of them was for 50 BMG rifles. I presume that the other one is more likely the one. From March 2019. Here's the information provided by DOD:

View attachment 7343942

That appears to be the “ASR” contract. Barrett is providing MRAD rifles in 338 and 300 Norma, so that’s not the 6 ARC contract.

 

[AccuSol-ERN]

Mac679,

Thanks for your service.

My champagne/beer comment was not directed at the DoD...….more geared towards JoeCivilian. Over the years it just seems like EVERY gun magazine has monthly issues on "improved" AR15 performance from new geewhiz cartridges. When the next logical step for cost-effective improved performance would be larger platform and common ammo.

For example, guys pushing their 6.5creeds to almost 6.5-284 velocity...…..never mind the hard bolt lift and brass is trashed after one firing...…..they get "great" speed though. Sure that is one way to get there......but doesn't seem logical.

Perhaps I am a naysayer dumbass......wouldn't be the first time......to each their own.

If the DoD put out an RFI and got what they wanted......cheers......go out and smoke some damn violent rioters to ballistic test.

Ern

 

[AMwood]

Okay got some more info, use at your own risk this is preliminary data. 103-110gr. These are Max loads, Drop 2gr or so to start.

8208xbr: 25.3gr
H4895: 25.5gr
LeverEvolution: 29.7gr (Best velocity)
AA2520: 28gr
RL-15: 27.8gr

Given that the sample loads above are in the ballpark of the Grendel, switching costs don’t seem all that great if a guy did want to switch up an existing 6.5 Grendel upper to squeeze the last bit of performance out of the platform.

Is it feasible to neck down existing Grendel brass to 6mm?

Modifying brass is new territory for me so apologies for the novice question. But if all it takes is a barrel, projectiles and dies, that makes a somewhat compelling argument for switching if you have piles of 6.5 brass and are using one of the powders above already.

 

[Ledzep]

Given that the sample loads above are in the ballpark of the Grendel, switching costs don’t seem all that great if a guy did want to switch up an existing 6.5 Grendel upper to squeeze the last bit of performance out of the platform.

Is it feasible to neck down existing Grendel brass to 6mm?

Modifying brass is new territory for me so apologies for the novice question. But if all it takes is a barrel, projectiles and dies, that makes a somewhat compelling argument for switching if you have piles of 6.5 brass and are using one of the powders above already.

The Grendel's shoulder is ~.030" further forward than the ARC, so you'll be sizing the neck and pushing the shoulder back at the same time. Which is fine, but it's going to make your case overall length grow, and you'll have to trim a lot of material.

You may also run into the base of the neck (near the neck/shoulder junction) being thicker than the rest of the neck. In the worst case you may need to neck turn or I.D. ream.

 

[long range sponge]

Commented on Hornady's video about barrel length and got this response. Not sure where testing was done but this gives an idea of the approximate velocities.

 

[stilesg57]

Keep in mind over on the FB 6mm ARC page people involved in this on the manufacturing side are sharing pictures of MVs. 11.5" barrels are pushing the 108s at 2324fps. Slow, but it's still hitting with 981ft-lbs at 200yds at sea level.

Hmmm...

Just thinking out loud here, but a 123gr 6.5 Grendel beats that energy figure, while putting more mass on target with higher sectional density and greater frontal area. Granted the energy and trajectory/wind deflection story probably favors the 6ARC at 500+, but neither is bringing a whole lot of fun to the party after that point anyway.

I guess 6.5G will have a little more recoil and another ~ounce of weight to carry per magazine, but otherwise I don’t see much hunting or warfighting benefit to the 6ARC. Definitely better in shooting sports and competition, I get that. The advantages are admittedly small on either side though.

Maybe my beloved Grendel shouldn’t be killed off just yet...or maybe I’m just rationalizing that because I have like 3 rifles chambered in it

 

[stilesg57]

Commented on Hornady's video about barrel length and got this response. Not sure where testing was done but this gives an idea of the approximate velocities.

View attachment 7343995

It actually surprises me how linear that graph is over such a wide number of barrel lengths. 5.56 doesn’t look at all like that.

 

[FatBoy]

As along time 6BR and 6 Dasher shooters 2900fps from a 28" barrel with 105+ gr bullets smacks of bullshit to me.

 

[FCS]

I can't get ASC mags to feed for shit with my Grendel. Hoping Elander is better.

I’ve had issues with both brands of magazines.
Basically I’ve had to test / prove out a magazine in lower(s) used for the 6 / 6.5 Grendel upper.
Magazines are the weak link for me with the Grendel based cartridges.
Once you find mags that work, GTG. Just keep them market and with correct lower. YMMV.

 

[Mopar man]

looks like a baby dasher

 

[yellowfin]

One wonders if the 6mm Lee Navy had been around at the time of more modern powders we'd still be shooting it today.

 

[Hollywood 6mm]

These are on the AR-15 platform . The upper is a 6GT and the rifle is a 22BR

And looking at the photos (plus knowing OAL limitations), I'd say you're running much lighter/shorter projectiles in them just to fit inside the mag length - something the ARC doesn't have an issue with. That's not even getting into bolt face issues.

Its interesting to see them crammed into an AR-15 pattern, but I'd say it looks like you're making some serious sacrifices to do it.

 

[Sutherlandsd]

6arc barrels are now available the proof ExpertVoice site. 16 and 18” cf and steel.

 

[Chaseerickson12]

Interested in a barrel for my origins action. Are any barrel manufacture spinning savage prefits?

 

[Foghornleghorn]

Precision Firearms has Criterion barrels in stock..

 

[SuperSneakySniper]

Omg i feel like if i keep waiting for a JP barrel im going to be left so far behind... then again, im finding it rather difficult to find all the other components i need to build an AR right now given the current craze.

 

[Gundoc]

 

[7mmShooter]

View attachment 7344398

Guessing 4DOF tables? Running it AB just now wasn't even close to that. The 14.5 table lined up pretty well at 2575fps mv... Which would be roughly 16" velocity.

 

[Ledzep]

4DoF and JBM (published G7 BC) are pretty much within 15fps all the way to 1000. Not sure what Lantac used for a BC in whatever calculator they used.

 

[Gundoc]

This is using the actual MV’s recorded at the range using 108 ELD-M in the barrel lengths listed. Then put into 4DOF. It’s using whatever Bc is in there. (Which hasn’t let me down using 6Creedmoor)
hasnt been trued yet using Axial Form Factor though. That may change the charts slightly.

 

[7mmShooter]

View attachment 7344440

View attachment 7344441

4DoF and JBM (published G7 BC) are pretty much within 15fps all the way to 1000. Not sure what Lantac used for a BC in whatever calculator they used.

AB is running within 5fps of both for 11.5 mv. (1049fps at 1000yd), thanks for the update Gundoc, that makes sense.

 

[slockwood]

Um, because they developed and tested it and it fit their needs for their mission set? You're assuming that this was all decided in theory and that the end user doesn't have a champagne budget and got the year and vintage they wanted after trying out a lot of bottles.

Keep in mind over on the FB 6mm ARC page people involved in this on the manufacturing side are sharing pictures of MVs. 11.5" barrels are pushing the 108s at 2324fps. Slow, but it's still hitting with 981ft-lbs at 200yds at sea level. My last tour in Afghanistan, the valley floor was 6600' above sea level. They wanted a good all around cartridge that would work from bad breath to 500-600m. Dropping the weight by 25% from an SR25 means less fatigue, guys can move further or get on an objective faster.

Yea the dude posting that stuff would be me as well as gundoc

I am going to true up the axial form factor on the 108s this weekend. With pre production ammo I was getting .91 we'll see what the most recent lot is running here soon.

 

[Ledzep]

This is using the actual MV’s recorded at the range using 108 ELD-M in the barrel lengths listed. Then put into 4DOF. It’s using whatever Bc is in there. (Which hasn’t let me down using 6Creedmoor)
hasnt been trued yet using Axial Form Factor though. That may change the charts slightly.

4DoF isn't a BC calculator and doesn't use BCs. There's a table of Cd vs. Mach and another table that describes the mass moments of inertia, CG, etc... for each bullet, among other things. My phone app 4Dof lines directly up with the screen shot of the web-based 4DoF I posted above (59 degrees, 29.93inHg, 0ft)

What's the elevation, baro, and temp you're using? I have to set my 4DoF to something like 1500ft on a 70 degree day and I'm in the ballpark of what was posted above. Most people are looking at sea level/STP for comparison sake.

 

[7mmShooter]

Personally the only reason I brought it up was because I've always had pretty similar results in the charts whether it be AB or 4DOF, first time I've seen one vary by that much, usually they're both within 15fps or so. Always learning

 

[Ledzep]

I'm pretty sure it's because of environmental inputs. Especially past 600yd it starts to vary quite a bit if people aren't putting the same data into the mix.

 

[7mmShooter]

True, I always compare at sea level to make things easier

 

[Yondering]

Um, because they developed and tested it and it fit their needs for their mission set?

Please don't spread bad info; it's already all over the place on this cartridge. The 6mm Grendel-based wildcats have been around at least 15 years for use with heavy long range bullets. The DOD may have adopted this one, but they did not develop it. Big difference. Hornady just bumped the shoulder back .030" from current wildcats; the only amazing thing is that it wasn't done at least 5 years ago.

Some of us who've been using these for a while are sitting back shaking our heads at the flurry of bad info being thrown around right now. I guess we knew it was coming though.

 

[Yondering]

My champagne/beer comment was not directed at the DoD...….more geared towards JoeCivilian. Over the years it just seems like EVERY gun magazine has monthly issues on "improved" AR15 performance from new geewhiz cartridges. When the next logical step for cost-effective improved performance would be larger platform and common ammo.

Dude, don't be that guy, acting like this is some brand new unproven round. Even 5 minutes of searching would show you this basic cartridge has been pretty well proven for quite a while. We know what those bullets can do at those speeds, and the basic cartridge (minus the .030" shoulder setback) has been proven to do that and more. It works well, and the only really new thing about it is factory ammo.

Necking down the 6.5 Grendel case to 6mm is one of the easiest wildcats ever done, and I suspect it was done about 5 minutes after the Grendel was first introduced. Of course this whole thing is only a slightly longer 6mm PPC with heavier bullets, and that one has been a proven winner for many many years. It's hard to take anyone seriously who feels they need to hold back to see if this'll be any good.

 

[Yondering]

Obviously, that's why I wrote that.... What's your point?

Sorry, I left off the whole second half of my post. We are in agreement but it sounds like I was arguing, my mistake.

Obviously it'll lose more velocity than the larger bore 6.5 Grendel when going to short barrels
BUT (the part I left off):

As you said it starts off with pretty good speed with the heavies as it is, and even if the heavy 105-108gr loads are down to the same speed as 123gr 6.5 Grendel in short barrels, they still have higher b.c. values and will shoot flatter with less wind drift, and do it with less recoil. (Not that the Grendel kicks much, but we're really talking about sight disturbance.)

I've got a couple 243 LBC rifles already (19" and 24"), but there's enough speculation about the short barrels that I ordered another blank yesterday and will be making my own 12.5". I'm not going to do the ARC chamber, since it would be easy to mix up ammo between the two cartridges, but final results should be more or less the same within a few fps anyway.

BTW as a data point, with max loads of Lever and the 105gr BTHP my 19" barrel loses only 90 fps to the 24". Those do run a little faster than Hornady's 6 ARC ammo, but only ~50 fps and that's due to using Lever and having the load tuned for my rifles only. Light bullets lose more speed than that, but that's not my interest with this cartridge. I expect to see the same load do 2400-2450 in the 12.5".

 

[Mac679]

Please don't spread bad info; it's already all over the place on this cartridge. The 6mm Grendel-based wildcats have been around at least 15 years for use with heavy long range bullets. The DOD may have adopted this one, but they did not develop it. Big difference. Hornady just bumped the shoulder back .030" from current wildcats; the only amazing thing is that it wasn't done at least 5 years ago.

Some of us who've been using these for a while are sitting back shaking our heads at the flurry of bad info being thrown around right now. I guess we knew it was coming though.

Would you like a cookie? And since you want to start with some semantics bullshit, DOD did not adopt this. The Army isn't going to it-NGSW is still a 6.8 caliber projectile last I checked. The Marines aren't adopting it. So that eliminates the two major players for small arms development within DOD, and the AF & Navy haven't adopted it either. A small element within DOD bought some guns and ammo but that doesn't equal DOD adoption. Please don't spread bad info.

See how that works both ways?

BTW, how many of those wildcatters spent the time and money to do the development (try not to get too offended over that word) for SAAMI adoption again? I didn't say that they invented 6mm type Grendel wildcats. I said they developed *this* cartridge.

 

[RMB]

Please don't spread bad info; it's already all over the place on this cartridge. The 6mm Grendel-based wildcats have been around at least 15 years for use with heavy long range bullets. The DOD may have adopted this one, but they did not develop it. Big difference. Hornady just bumped the shoulder back .030" from current wildcats; the only amazing thing is that it wasn't done at least 5 years ago.

Some of us who've been using these for a while are sitting back shaking our heads at the flurry of bad info being thrown around right now. I guess we knew it was coming though.

Yes, I was wondering how Robert Whitley (sp?) et. als. that worked on the development of the 6mm AR/LBC/Etc. feel about this "new" development? I guess the difference is connections, money and marketing.

 

[MPrimo]

As a consumer that doesn't handload, it doesn't matter to me. I don't really understand the vitriol. If we can improve performance for the masses and not just the folks willing to form brass and experiment on their own, then we all win. Move on to the next wildcat if that's your passion ... that makes the game better for everyone as well (as it seems to have done here).

Oh snap ... I'm arguing with the internet again ... my bad!

 

[hereinaz]

So I wonder if proof is going to start cranking out barrels for it? If so I’ll probably go ahead and get on the 6month wait lol. Looks like the proof will be a 7.5 twist I wonder if that will stabilize the 108s in a 16 or 18” barrel?

I know Evolved Ballistics put in a preorder for 6mm ARC barrels from Proof.

 

[hereinaz]

I think anything shorter than 20” is giving up too much burn time/velocity for any of the smaller caliber grendel
Variants . My 20” 22 grendel test barrel yielded good velocity with 75 elds

I am planning at 22 grendel bolt gun in a mini action.

What velocity were you getting?

 

[slockwood]

I am planning at 22 grendel bolt gun in a mini action.

What velocity were you getting?

I know this wasnt directed at me but my 28" bolt 224 grendel pushes the 88eld around 3k using n550. 6.5 twist krieger barrel.