New 6mm Advanced Rifle Cartridge

@Yondering yup I've done the same with blue loctite before also.
I know a few people that have had good luck with Odin barrels for 3 gun, but in more standard configurations, and in 223 obviously. They seem well made but apparently making a part well is entirely different than actually understanding what you're doing.
I just bought a pound of Lever based on all the success I've seen with it on here lately. I'm not displeased with CFE but I'm a sucker for trying new things. I even keep buying Nosler RDF's when they come out with new ones. Someday I'll learn.
How does Lever do in 223 loads?

One thing I’ve seen repeatedly with Lever is that it generally gives very low ES/SD at top end loads. Usually with heavy for cartridge bullet weights. I used CFE223 more before trying Lever but didn’t see the same trend with that one, despite them being somewhat similar.

As for Lever in 5.56, like the ARC it’s faster than anything else, from 65gr and up anyway. Most of y’all would think I’m nuts if you heard the speeds I’m getting, but this 20” tube is doing mid 2900’s with several 73/75/77gr bullets and good brass life using Lake City.

This (Lever and this 20” barrel) is actually the first time I’ve gotten halfway decent groups with the 70gr RDF; the combination of Lever and a long 2.355” OAL (using a cut mag like you’ve shown) has made the difference between shotgun patterns and roughly MOA groups. Speed with that load is 3160 fps with single digit SD; crazy of course and try at your own risk, NOT a load for an inexperienced loader to try, but it has some promise for this rifle as a way to shoot the RDF accurately. It still shoots poorly at 2.255” though.
Also I’ve been working on an idea to cut the mags further down for a functional 20 rds without the cut being exposed. Will share details with you at some point.
 
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I tried it

I tried it with 88s in 223, it was 50-75 fps slower than Varget, and very compressed to get there. Tried it in 6mm Grendel, which is very close to 6mm ARC, and again couldn't pack enough in there to get velocity up, about like the . Just too small of a case for that bulky of a powder. With the big case like the 30/06, you can get enough in the case to be scary, but should see decent velocity without having to push pressure. My 6mm Grendel results are comparable to that new 6mm ARC data on the Winchester page, I was referring to the Hodgdon Reloading data for 224 Valkyrie which shows it is faster than CFE223 with 90s...that never happened. Without a hydraulic press to seat bullets.

I ran some StaBall in one of my Creedmoors the other day. In terms of velocity for visual pressure, it ran right with RL16, about a grain higher. It's quite a bit less bulky than RL16, but that's not saying much, still bulkier than I was expecting for a ball powder. Given that, per Hodgdons burn rate chart, it falls between the 4350 and 4831 range it certainly makes sense that it would work better in larger cases than something like the ARC or .223.

I downloaded the GRT to play with, and while it seems to do a pretty good job predicting my measured velocities with RL16 and RL26 over a few different rifles, its StaBall estimates are just as far off what I'm seeing as QL.

Been keeping an eye out on all the sites, and the Discord feed, plenty of other powders have come and gone, but no LVR to be found anywhere ☹️
 
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One thing I’ve seen repeatedly with Lever is that it generally gives very low ES/SD at top end loads. Usually with heavy for cartridge bullet weights. I used CFE223 more before trying Lever but didn’t see the same trend with that one, despite them being somewhat similar.

As for Lever in 5.56, like the ARC it’s faster than anything else, from 65gr and up anyway. Most of y’all would think I’m nuts if you heard the speeds I’m getting, but this 20” tube is doing mid 2900’s with several 73/75/77gr bullets and good brass life using Lake City.

This (Lever and this 20” barrel) is actually the first time I’ve gotten halfway decent groups with the 70gr RDF; the combination of Lever and a long 2.355” OAL (using a cut mag like you’ve shown) has made the difference between shotgun patterns and roughly MOA groups. Speed with that load is 3160 fps with single digit SD; crazy of course and try at your own risk, NOT a load for an inexperienced loader to try, but it has some promise for this rifle as a way to shoot the RDF accurately. It still shoots poorly at 2.255” though.
Also I’ve been working on an idea to cut the mags further down for a functional 20 rds without the cut being exposed. Will share details with you at some point.
....that's an interesting note about using Lever for 5.56 loads, I just checked the Hodgdon site and Lever isn't even one of the powders listed for that caliber. Not to say it isn't valid, especially as your experience has proven. I tend to lean towards purchasing powders that work for multiple calibers if possible and hearing Lever can be used for 5.56 is encouraging.
 
....that's an interesting note about using Lever for 5.56 loads, I just checked the Hodgdon site and Lever isn't even one of the powders listed for that caliber. Not to say it isn't valid, especially as your experience has proven. I tend to lean towards purchasing powders that work for multiple calibers if possible and hearing Lever can be used for 5.56 is encouraging.
Yeah Lever is an interesting one; it works really well for a lot of different cartridges but has published data for very few of them. Most of the progress with Lever is from wildcatters experimenting with it. (I am a wildcatter myself but others were using Lever before I was so I don’t take any credit for that. Except maybe in the 20 Tac, I don’t know if anyone else using it there but it’s the best I found.) I do admit to more willingness to experiment than most, because I’m a test and development guy at my core; always felt it’d be a sweet job to run load development in a lab for one of the major companies.

This 6mm ARC is an example; a number of us wildcatters were using it for the various 6mm Grendel versions for at least 3-4 years before the ARC came around. Given the lack of data (still) for Lever in other cartridges using the same group of powders as the ARC, I have to think Hornady included Lever data for this one specifically because of so many wildcatter’s success with it.

I’ve personally had great results with Lever in the following cartridges:
20 Tactical
5.56
243 LBC
6.5 Grendel
30 Herrett / SPC
308 Win
358 Herrett
35 Remington
35 Whelen

Maybe a couple more I’m forgetting at the moment. It’s a pretty versatile powder if your goal is highest velocity with heavier bullets and low ES/SD. It does trade off temp sensitivity in a lot of loads, but that varies with the load and some do a lot better than you’d think.

Experiment at your own risk of course and be safe. It’s definitely possible to go over pressure with it, but it’s relatively mild mannered at the top end in my experience, not like 8208 or RL17 that spike hard when you hit max.
 
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Quick question... I don't have any dies yet but I think this brass listed below can be used to form your own 6mm ARC cases. Anybody know for sure?

You can, but it’s a lot of forming to do. You’re necking down from roughly .44 cal to .243 cal so plan on multiple steps with a couple annealing stages in the process.

IMO, just get some of their standard Grendel brass back ordered; it’s quite a bit cheaper anyway and is excellent brass. I did that this past fall and ended up with my brass in a month or two.

Personally I’d rather form brass from 7.62x39 than neck down basic brass. That’s not ideal; you end up with the weaker large primer pocket and usually lower quality brass, but it does work if you’re hard up for brass. I’ve got a couple hundred pieces of that myself from previous lean times.

A couple tips if you do it, either way:
- use FL dies to neck down rather than bushing dies. It works easier/better and can neck down in larger steps.
- I’ve had good success necking 7.62x39 down in a Hornady 6.5 Grendel FL die for the first step, then a cheap Lee 6mm PPC die for the second step. Basic brass needs some other steps first, like 35 cal and then 30 cal (9.
- anneal after the neck down, not before. Annealing the shoudoes help the case fireform better too.
- check the neck thickness; some brass can end up with thick or lopsided necks.

Also avoid S&B 7.62 brass; the primer pockets are too shallow and it’s not worth the trouble to cut them correctly.
 
Very, very interesting to learn about Lever having use in 5.56 as well. Lever had my curiosity, but now it has my attention. I know the 6ARC temp swing data may still be in infancy, but do you have any data collected on how it’s faring for you in that 20” with 77’s?
 
Quick question... I don't have any dies yet but I think this brass listed below can be used to form your own 6mm ARC cases. Anybody know for sure?

I looked at that as a starting point as well., but just used their Grendle Brass. Its a single pass and trim. Good results. See my earlier post for tips. Ship time for Starline is a variance. my first order of 250 for testing was a couple weeks, 500 more took a month.
 
Interested in the 12.5 Lilja, what kind of accuracy is to be expected?

dont have a range farther than 300 sadly so kinda like the idea of putting this on a sbr lower
I'll start w/the disclaimer here. I own Six Sigma Arms and have Lilja produce these barrels as an exclusive offering from us. We also have Lilja cut us barrels for the 6.5mm Grendel.

The jury is still out on the 6mm ARC barrels. These just started showing up in customer's mailboxes last week and I've yet to hear any feedback. Our personal test barrels have been consistent with our 6.5mm Grendel Lilja barrels. A build done correctly will easily result in sub-MOA performance. We're routinely seeing results less than 1/2-MOA.

Of course, results do vary and barrels are, in a way, like women. Some are pretty ti... Um, never mind. Performance can and will vary. That said, if you get one that shoots poorly, I want to know about it so we can get it taken care of. With all the Lilja barrels that we've sold, I've only received negative feedback once (it was shooting about 1.5-MOA) and that turned out to be an issue with the customer's build that was easily corrected once I had it in the shop (gas tube indexing issue if I remember correctly).

Please let me know if you have any questions. I'm happy to help.
-Curt
 
I'll start w/the disclaimer here. I own Six Sigma Arms and have Lilja produce these barrels as an exclusive offering from us. We also have Lilja cut us barrels for the 6.5mm Grendel.

The jury is still out on the 6mm ARC barrels. These just started showing up in customer's mailboxes last week and I've yet to hear any feedback. Our personal test barrels have been consistent with our 6.5mm Grendel Lilja barrels. A build done correctly will easily result in sub-MOA performance. We're routinely seeing results less than 1/2-MOA.

Of course, results do vary and barrels are, in a way, like women. Some are pretty ti... Um, never mind. Performance can and will vary. That said, if you get one that shoots poorly, I want to know about it so we can get it taken care of. With all the Lilja barrels that we've sold, I've only received negative feedback once (it was shooting about 1.5-MOA) and that turned out to be an issue with the customer's build that was easily corrected once I had it in the shop (gas tube indexing issue if I remember correctly).

Please let me know if you have any questions. I'm happy to help.
-Curt
Curt, what did the gas tube have to do with it?? What was the issue?? By "Indexing" do you mean it was touching the upper receiver by putting pressure on it?? Thanks!!
 
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Curt, what did the gas tube have to do with it?? What was the issue?? By "Indexing" do you mean it was touching the upper receiver by putting pressure on it?? Thanks!!
Correct. This specific one was out of alignment enough that the gas tube was even putting pressure on the gas key. If groups were shot slowly and everything was allowed to throughly cool between shots, the groups were near acceptable. How sustainable this would have been over time is debatable and certainly not worth the time/effort/ammo to find out. This gun used an adjustable clamp on style gas block and it was tweaked enough that it was even cutting off a good deal of gas, enough that the block was adjusted to run pretty much wide open.

I ended up tearing down the entire upper and giving it a good once over to make sure that everything was in-spec. I lapped the receiver, bedded the barrel during reassembly, and set the torque to a value that has produced good results with barrels of this length/profile in the past. I ended up replacing the gas tube as well since the initial one had been subjected to some awkward stress. After all of this the barrel settled right in and shot great.

Examples like this are why I point out that the build needs to be done correctly. I offer free assembly with barrel purchases for this very reason, even if customers don't purchase the rest of the upper parts from me. My primary concern is that the barrel delivers the expected results and, especially for inexperienced customers, doing the assembly for them helps make this happen.
 
Correct. This specific one was out of alignment enough that the gas tube was even putting pressure on the gas key. If groups were shot slowly and everything was allowed to throughly cool between shots, the groups were near acceptable. How sustainable this would have been over time is debatable and certainly not worth the time/effort/ammo to find out. This gun used an adjustable clamp on style gas block and it was tweaked enough that it was even cutting off a good deal of gas, enough that the block was adjusted to run pretty much wide open.

I ended up tearing down the entire upper and giving it a good once over to make sure that everything was in-spec. I lapped the receiver, bedded the barrel during reassembly, and set the torque to a value that has produced good results with barrels of this length/profile in the past. I ended up replacing the gas tube as well since the initial one had been subjected to some awkward stress. After all of this the barrel settled right in and shot great.

Examples like this are why I point out that the build needs to be done correctly. I offer free assembly with barrel purchases for this very reason, even if customers don't purchase the rest of the upper parts from me. My primary concern is that the barrel delivers the expected results and, especially for inexperienced customers, doing the assembly for them helps make this happen.
Little tid bits of information like this are a big reason I take the time to read an entire thread when preparing for a new project or build. Thank You!
 
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Bought my barrel the da they came out on brownells, just now having the chance to work with some loads.

was looking for a 16” AR that hit hard out to 300 for coyote hunting. So my loads are based on that end state in mind.

(all speeds done with Mag V3)

Factory:

black 105s
FPS:2444
GRP: 1.5”

match 108s
FPS:2502
GRP: 1.3”

87-gr VMAX
30.5gr CFE-223
FPS: 2746
GRP: 3”

87-gr VMAX
29.7gr VARGET

FPS: 2745
GRP: 1.1”

95-gr S-TMK
30gr CFE-223
FPS: 2646
GRP: 2.5”



So for what ever reason, CFE just wouldn’t shoot for me. Barrel has ~100 rounds down it, so just getting broken in IMHO.

2800 FPS with an 85-90 grain bullet in a 16” gun was the goal when starting this. If anybody has any suggestions on powders, id appreciate it. Thanks.
 
I'm looking to getting into PRS this summer against the big bolt boys. Wanted to try a AR15 6mm ARC build to see if I can be at least semi-competitive. Anyone have advice on what length I should be looking to get?

My initial thoughts were a 20" Carbon Fiber Proof, or a 22" Bartlein.
 
I'm looking to getting into PRS this summer against the big bolt boys. Wanted to try a AR15 6mm ARC build to see if I can be at least semi-competitive. Anyone have advice on what length I should be looking to get?

My initial thoughts were a 20" Carbon Fiber Proof, or a 22" Bartlein.
Don't do a CF barrel for PRS. Weight is your friend.
 
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I submitted my order to craddock for a 18in barrel today. Is anyone running a piston kit or just DI? I got a new Superlative rifle length kit sitting in a drawer that I want to try. But didnt know if it’s been done yet. I’ll also be running a JP buffer spring so I can tune it if need be.
 
Correct. This specific one was out of alignment enough that the gas tube was even putting pressure on the gas key. If groups were shot slowly and everything was allowed to throughly cool between shots, the groups were near acceptable. How sustainable this would have been over time is debatable and certainly not worth the time/effort/ammo to find out. This gun used an adjustable clamp on style gas block and it was tweaked enough that it was even cutting off a good deal of gas, enough that the block was adjusted to run pretty much wide open.

I ended up tearing down the entire upper and giving it a good once over to make sure that everything was in-spec. I lapped the receiver, bedded the barrel during reassembly, and set the torque to a value that has produced good results with barrels of this length/profile in the past. I ended up replacing the gas tube as well since the initial one had been subjected to some awkward stress. After all of this the barrel settled right in and shot great.

Examples like this are why I point out that the build needs to be done correctly. I offer free assembly with barrel purchases for this very reason, even if customers don't purchase the rest of the upper parts from me. My primary concern is that the barrel delivers the expected results and, especially for inexperienced customers, doing the assembly for them helps make this happen.
Thanks for the reply Curt!! I have one other question. When tightening a barrel nut how important is it to torque it?? Some I have done use hand guards where you have to have the barrel nut in a specific spot to line up the handguard. So it may have to be tightened a touch more. So does these hurt anything as long as it it good and tight???
 
Thanks for the reply Curt!! I have one other question. When tightening a barrel nut how important is it to torque it?? Some I have done use hand guards where you have to have the barrel nut in a specific spot to line up the handguard. So it may have to be tightened a touch more. So does these hurt anything as long as it it good and tight???
This comes down to luck and your expectations. There are more ways than 1 to tune barrel harmonics but torque is one of the easiest, fastest, and most consistent ways to do it. For that reason, on a precision build, I never use a barrel nut that requires indexing for the gas tube. If I'm forced to (and don't get lucky), I'll cut it to give me clearance where it NEEDS to be and/or use shims to get torque where I want it.

Luck and expectations are in a similar vein here. If you're starting with a high quality barrel like a Lilja/Krieger/Bartlein/Shilen/Whatever and you're expectations are to shoot 1-MOA groups, you'll probably hit that number as long as your torque is "acceptable". If you have higher expectations though, like sub 1/4-MOA, now everything (including torque) starts to matter a LOT more. Can you get a gun to shoot 1 hole cloverleafs off chance? Sure, I have an all factory Bushmaster Varminter that shoots lights out but it's certainly an exception to the rule. I got lucky. When you're aiming for tiny bug-holes, the little things get exponentially more important.

We build enough based on our custom Lilja barrels that I can give you a pretty tight window of what torque values to start with. Chances are, your barrel is going to tune in +/-2 lbs of that starting point (if you add a compensator or another type of heavy muzzle device that starting point will change).
 
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This comes down to luck and your expectations. There are more ways than 1 to tune barrel harmonics but torque is one of the easiest, fastest, and most consistent ways to do it. For that reason, on a precision build, I never use a barrel nut that requires indexing for the gas tube. If I'm forced to (and don't get lucky), I'll cut it to give me clearance where it NEEDS to be and/or use shims to get torque where I want it.

Luck and expectations are in a similar vein here. If you're starting with a high quality barrel like a Lilja/Krieger/Bartlein/Shilen/Whatever and you're expectations are to shoot 1-MOA groups, you'll probably hit that number as long as your torque is "acceptable". If you have higher expectations though, like sub 1/4-MOA, now everything (including torque) starts to matter a LOT more. Can you get a gun to shoot 1 hole cloverleafs off chance? Sure, I have an all factory Bushmaster Varminter that shoots lights out but it's certainly an exception to the rule. I got lucky. When you're aiming for tiny bug-holes, the little things get exponentially more important.

We build enough based on our custom Lilja barrels that I can give you a pretty tight window of what torque values to start with. Chances are, your barrel is going to tune in +/-2 lbs of that starting point (if you add a compensator or another type of heavy muzzle device that starting point will change).
I believe you answered my question. But I was referring to a "Hand guard" not the actual barrel nut where the gas tube does run through the nut. The Guntec hand guard has to be "Timed" to the barrel nut. What do you recommend as a good starting point to torque the barrel?? I also have a tool to lap the upper receiver. One last question, how do you keep the clearance between the upper and the barrel extension to a bare minimum?? Do you shim it with something??? I really appreciate all of your input!! Thanks again!!
 
I'd go 24-26" for PRS with the ARC. Factory 108's will be doing 2750-2800fps which will put you in a similar realm to the guys running dashers and shorter barreled GT's.
Agreed. My 6mm Grendel are 26" with +2" gas. The nodes are about the same velocity as a 24", but pressure is about 2K to 3K less, which is 2K to 3K less pressure than a 22", etc etc
 
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Bought my barrel the da they came out on brownells, just now having the chance to work with some loads.

was looking for a 16” AR that hit hard out to 300 for coyote hunting. So my loads are based on that end state in mind.

(all speeds done with Mag V3)

Factory:

black 105s
FPS:2444
GRP: 1.5”

match 108s
FPS:2502
GRP: 1.3”

87-gr VMAX
30.5gr CFE-223
FPS: 2746
GRP: 3”

87-gr VMAX
29.7gr VARGET

FPS: 2745
GRP: 1.1”

95-gr S-TMK
30gr CFE-223
FPS: 2646
GRP: 2.5”



So for what ever reason, CFE just wouldn’t shoot for me. Barrel has ~100 rounds down it, so just getting broken in IMHO.

2800 FPS with an 85-90 grain bullet in a 16” gun was the goal when starting this. If anybody has any suggestions on powders, id appreciate it. Thanks.
From what I have seen on here, Lever Revolution is the powder to go with.
 
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With all the great info here, I called up CLE to change my 6 ARC barrel order from a +1, 22 inch barrel to a regular rifle length 24" barrel. The BA barrel I ordered to have something to shoot and to test some loads while waiting for the CLE barrel is supposed to show up today so hopefully I can go fire some factory rounds Friday to get some brass to reload.

I had some powder luck yesterday and got to order some BL-C2 and H380 to test out. Will keep looking for Leverevolution but I read a thread somewhere by a guy testing BL-C2 for his ARC with 105 grain bullets and was pretty happy with the results.

For those forming 6 ARC from Lapua 6.5 Grendel brass, have you found the need to neck turn after forming since the brass in the necks would probably get thicker?
 
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Reforming Starlines here. one guy on here recently suggested I test neck tension. On a fired case a bullet does have a tad bit of tension when seating it and pulling it with fingers. Lapua may be different. I'm on the fence about neck turning, If I had the turning tools I'd just go ahead and do it.
 
You’ll need a telescoping bore gauge and a micrometer, or a set of pin gauges.

On a related note - precision measuring tools are not cheap.
Forster publishes their dimensions on their website. But they don't make 6ARC dies yet. I was wondering in a one off if anyone happened to know...or possibly already own those tools...
 
For those forming 6 ARC from Lapua 6.5 Grendel brass, have you found the need to neck turn after forming since the brass in the necks would probably get thicker?
Unless your chamber has a tight neck, or you’re forming from 7.62x39, you shouldn’t need to neck turn because of thick necks. Occasionally it’s needed when forming from x39 brass.

With that said, I generally do neck turn even my Lapua brass to ensure every piece is as consistent as possible. Also with a lathe it’s fairly easy to do.
 
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With all the great info here, I called up CLE to change my 6 ARC barrel order from a +1, 22 inch barrel to a regular rifle length 24" barrel. The BA barrel I ordered to have something to shoot and to test some loads while waiting for the CLE barrel is supposed to show up today so hopefully I can go fire some factory rounds Friday to get some brass to reload.

I had some powder luck yesterday and got to order some BL-C2 and H380 to test out. Will keep looking for Leverevolution but I read a thread somewhere by a guy testing BL-C2 for his ARC with 105 grain bullets and was pretty happy with the results.

For those forming 6 ARC from Lapua 6.5 Grendel brass, have you found the need to neck turn after forming since the brass in the necks would probably get thicker?
My son in law has a Ballistic Advantage barrel and we had to turn the necks on the Lapua brass. You could fire it but the accuracy sucked!! I figured the problem was problem high pressure for to tight of neck tension. I took a fired case and tried to push a bullet in by hand and it would NOT go in. In reality it was only like a .001 thicker than the Starline brass. But in a tight throat that is .002 to much neck tension and will not let the case neck expand inside the chamber. With cold weather if has been put on the back burner for now. I hope to be getting my Shaw barrel in the next month. Not sure how that will shoot. I have read mixed reviews about them, just hoping for the best......