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New 6mm Advanced Rifle Cartridge

Until my Lilja barrel arrives I have settled on a 108ELD load running 2,576 out of a 20” AB barrel. 13.3 mils to 1100 and holds 1/2 MOA if I can deal with the wind. This load falls right between my Grendel and 308, the 23” barrel will help but I still don’t think it will run the same ballistics as my 155 Scenars do.
 
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That definitely does not match what I'm measuring, on anything except actual small base dies (not Hornady). All my other dies including Hornady don't size the base diameter very much (less than .001") on minimum spec chambers, because it's not needed. However, some size the shoulder diameter more than others, and Hornady dies are one of those, in most cases sizing the shoulder diameter .004"-.006" smaller, compared to Forster and others at only .002"-.004" depending on the cartridge. Interestingly, the Lee dies I'm measuring (including my 6 PPC dies which work for the 6 ARC and other 6mm Grendel-based wildcats) size the shoulder diameter less than Hornady and are closer to Forster dimensions. That Lee 6 PPC FL size die actually works very well for my 243 LBC chambers, matching the body dimensions closely.
When I say shoulder diameter, I'm referring to the body diameter at the shoulder/body junction, just using fewer words.

Based on that, I don't consider Hornady dies to be small base dies like what RCBS makes. IMO true small base dies that size the base diameter down more than needed for most chambers are a detriment to accuracy. I've achieved very good accuracy with Hornady dies though, if care is put into getting low rounout and adjusting dies to match the shoulder datum dimension in the chamber.
YMMV.
The PPC at the shoulder is smaller than the ARC or Grendel. That may be why those dies size the shoulder smaller.
Everyone is free to use whatever they want. Every person should be capable of measuring the diameter of brass after they size it. Every person that wants to buy 2 sets of dies can easily compare them.
I guess I'm not going to criticize someone for using small base dies when I use Hornady which I know sizes the brass to the same size. Use whatever you want it isn't going to effect my brass.
 
So, CMMG is quoting 10+ weeks now, when I was originally quoted 2-4...
If I’m gonna wait that long I may as well pay a little more and make it worth it.

Odin Works? Craddock? X-Caliber?
Any recommendations?
 
@awpk03s From the choices listed, Based solely on reputation, I’d go with a bartlein blank from craddock... I’ve got a 6.5 Grendel from Odin and it’s a shooter, but rep has me expecting more from craddock.

JP is another quality option I wouldn’t overlook.
 
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So, CMMG is quoting 10+ weeks now, when I was originally quoted 2-4...
If I’m gonna wait that long I may as well pay a little more and make it worth it.

Odin Works? Craddock? X-Caliber?
Any recommendations?
got my 18" odin barrel this weekend (pre ordered in mid June), but they forgot to put the included XL gas tube in when they shipped it otherwise I would have had a few down range by now...the last I heard from them, was the 21" barrels were getting ready to ship to pre orders, and they might list a few on their website once those orders are filled? if I had the $ and patience I would have waited for craddock, only hear good things about them
 
My 243LBC AR 40deg will hold 20-shot group about 1.5 to 2.0 moa at 600yd with a muzzle velocity of 2750 with the Nosler 105CC. I had the opportunity to test at 1000yd and the results were disappointing, for some reason muzzle velocity was slightly higher at 2770 (higher temps at 80); 20-shot group was about 3moa and terminal velocity of about 1250fps.
 
got my 18" odin barrel this weekend (pre ordered in mid June), but they forgot to put the included XL gas tube in when they shipped it otherwise I would have had a few down range by now...the last I heard from them, was the 21" barrels were getting ready to ship to pre orders, and they might list a few on their website once those orders are filled? if I had the $ and patience I would have waited for craddock, only hear good things about them
Let us know how your 18’ shoots. I’ve got one of their 21" barrels on order. Hopefully they include the gas block and tube with my order.
 
The PPC at the shoulder is smaller than the ARC or Grendel. That may be why those dies size the shoulder smaller.
Everyone is free to use whatever they want. Every person should be capable of measuring the diameter of brass after they size it. Every person that wants to buy 2 sets of dies can easily compare them.
I guess I'm not going to criticize someone for using small base dies when I use Hornady which I know sizes the brass to the same size. Use whatever you want it isn't going to effect my brass.

Hornady brass doesn't size the base to the same size as small base dies. Saying they are small base dies is bad info. They size the shoulder smaller than others, but not the base. Small base dies size the base smaller as well and that is the significant difference; the hint is in the name.

You're incorrect about the PPC as well; it's slightly larger at the shoulder than the Grendel, but only by .001". Not enough to be very significant when dies are reducing that dimension .004-.006".
 
Hornady brass doesn't size the base to the same size as small base dies. Saying they are small base dies is bad info. They size the shoulder smaller than others, but not the base. Small base dies size the base smaller as well and that is the significant difference; the hint is in the name.

You're incorrect about the PPC as well; it's slightly larger at the shoulder than the Grendel, but only by .001". Not enough to be very significant when dies are reducing that dimension .004-.006".
Funny you have been using small based dies all this time and didn't know it but you criticize others for buying small base dies.
Anyone can find this info with just a few phone calls. Call every die company and ask to speak to the engineer. Ask them what their target design diameter for the dies are. Yes they all have tolerances and may be a little larger or small but they draw the dies to be made a certain size(target dia). Ben At Hornady has been making custom dies for me 50 at a time for years and Lonnie before him going back 15 years. Either on of those guys can tell you in 2 seconds .004 under minimum chamber size.
 
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Can anyone out there explain why fireform rounds are so accurate? I mean we just use any old powder and powder charge with the cheapest POS bullet we have on the shelf and sometimes they turn out to be as accurate as the final load we work up after 2 weeks with a certain powder and charge whittled down to the nearest .01 gr and what we believe to be the best bullet choice.
Why are some chambers so easy to find a good load or loads for and some are a royal pain in the ass to find any load that works well? Chamber design yes but what part?
Ah well, using small base dies doesn't concern me a bit.
 
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@awpk03s From the choices listed, Based solely on reputation, I’d go with a bartlein blank from craddock... I’ve got a 6.5 Grendel from Odin and it’s a shooter, but rep has me expecting more from craddock.

JP is another quality option I wouldn’t overlook.
Is JP making a 6 ARC option?
 
Is JP making a 6 ARC option?
I thought I had read somewhere that they were, but it is not on their site. That said, they make a 6.5 grendel and a 224 valkyrie, so I would be a bit surprised if they didn't jump on this newest and greatest.
 
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I cancelled the CMMG upper and ordered an Odin 21” complete upper. I think I will be happier with this solution, even if it’s a longer wait. I just can’t justify the additional $400-500 for the Craddock/Bartlein upper, as much as I’d like to.
 
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got my 18" odin barrel this weekend (pre ordered in mid June), but they forgot to put the included XL gas tube in when they shipped it otherwise I would have had a few down range by now...the last I heard from them, was the 21" barrels were getting ready to ship to pre orders, and they might list a few on their website once those orders are filled? if I had the $ and patience I would have waited for craddock, only hear good things about them

Should be a soft shooter, but may require some tweaking of the buffer system. A +2 on an 18” is a bit much.
 
I cancelled the CMMG upper and ordered an Odin 21” complete upper. I think I will be happier with this solution, even if it’s a longer wait. I just can’t justify the additional $400-500 for the Craddock/Bartlein upper, as much as I’d like to.
That sounds like a good move. I would be pissed if I was getting the results that dude in video was getting.
 
That sounds like a good move. I would be pissed if I was getting the results that dude in video was getting.
I agree, what I find surprising is how many people thought those results were great. One commenter even said that "very, very, very few AR’s shoot sub Moa". I have to remind myself how many people in the shooting world have no interest in precision shooting.
 
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Should be a soft shooter, but may require some tweaking of the buffer system. A +2 on an 18” is a bit much.
Yeah I was sort of leery about that aspect, we'll see when the tube gets here. I can just slip 0.101 diameter drill bit (#38?) into the gas port. Called them today, supposedly will ship the gas tube out this afternoon.
 
for those shooting the Hornady 105 BTHP Black ammo: the 105 BTHP ammo is to long. Hornady is aware of it now after one of our customers discovered the issue and we confirmed it along with several other users and manufacturers barrels. You will likely be in the lands and grooves. Your going to have to reseat the 105 to 2.1 COAL from the factory 2.247 or 2.25. This is not a chamber issue, only the first two batches of ammo. The new ammo will be set to 2.22 COAL on any future batches. If you have dies for 6.5 or 6mm you can reseat the ammo and it works fine. Our 24" at 575 yards was doing a .17 MOA, the ammo is good, just to long.
 
for those shooting the Hornady 105 BTHP Black ammo: the 105 BTHP ammo is to long. Hornady is aware of it now after one of our customers discovered the issue and we confirmed it along with several other users and manufacturers barrels. You will likely be in the lands and grooves. Your going to have to reseat the 105 to 2.1 COAL from the factory 2.247 or 2.25. This is not a chamber issue, only the first two batches of ammo. The new ammo will be set to 2.22 COAL on any future batches. If you have dies for 6.5 or 6mm you can reseat the ammo and it works fine. Our 24" at 575 yards was doing a .17 MOA, the ammo is good, just to long.
Good info.
 
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for those shooting the Hornady 105 BTHP Black ammo: the 105 BTHP ammo is to long. Hornady is aware of it now after one of our customers discovered the issue and we confirmed it along with several other users and manufacturers barrels. You will likely be in the lands and grooves. Your going to have to reseat the 105 to 2.1 COAL from the factory 2.247 or 2.25. This is not a chamber issue, only the first two batches of ammo. The new ammo will be set to 2.22 COAL on any future batches. If you have dies for 6.5 or 6mm you can reseat the ammo and it works fine. Our 24" at 575 yards was doing a .17 MOA, the ammo is good, just to long.

So reseat to 2.1” or 2.22”?
 
So reseat to 2.1” or 2.22”?
I set all mine back to 2.185. Sixty round remand from the batch that i bought. Will be re-shooting them this coming weekend. I did not have the problems other shooters had (semi-auto shooters). Mine is a bolt gun.
 
. Our 24" at 575 yards was doing a .17 MOA, the ammo is good, just to long.

(y)
ammo is clearly good but shooter is also. This has been my experience with this cartridges' parents - 6PPC and 6.5G - the design is a real winner, with precision just 'very easy'.
 
Pictures added
 

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Anybody here tried AR-Comp yet? I'm surprised it wasn't in the load data. It's what Alliant suggested as a potential fit re: temp-stable powders, even though they hadn't done their own testing yet.
 
Not sure on JP, but another high end barrel maker doing 6ARC is Proof
Guys, I just bumped into another builder making 6ARCs: Seekins Precision:


Relevant stats on their build:
- 22" barrel
- 8 twist
- nice hardware on the rest of the setup
 
Compass Lake is also going to offer barrels. They have them up for preorder. I think Craddock has them too.
 
Found this as I was surfing this afternoon...has this been discussed? TAP 106 grain...claims it has temp stable powder w/ flash retardant...I would guess proprietary? If you go to that link, they have thumbnails and data table with barrier penetration numbers
HornadyTAP106gr.JPG
 
Found this as I was surfing this afternoon...has this been discussed? TAP 106 grain...claims it has temp stable powder w/ flash retardant...I would guess proprietary? If you go to that link, they have thumbnails and data table with barrier penetration numbers

Hadn't seen that one. I hope they get a manufacturer or two to put out some powder to match for the reloaders out here. It'd probably make a good powder for various cartridges, so we'll see if there's interest.
 
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Can i use a 6mm PPC Neck Sizing Die to resize the 6mm ARC Brass? I have a Uintah Precision Upper on a AR-15 Lower. I have taken the fired brass and head space measures at 1.1910 (SAAMI Spec: 1.1901 - 1.2001) Fired Brass fits in a Wilson 6mm ARC Case Gauge. i'm assuming i have a tight chamber and all i really need to do is re-size the neck. Fired case does chamber in the action without any effort. I have reached out to Forester and they said they will get back to me.
 
Can i use a 6mm PPC Neck Sizing Die to resize the 6mm ARC Brass? I have a Uintah Precision Upper on a AR-15 Lower. I have taken the fired brass and head space measures at 1.1910 (SAAMI Spec: 1.1901 - 1.2001) Fired Brass fits in a Wilson 6mm ARC Case Gauge. i'm assuming i have a tight chamber and all i really need to do is re-size the neck. Fired case does chamber in the action without any effort. I have reached out to Forester and they said they will get back to me.

I just got a reply back from Forester concerning my question on using their neck sizing die for the 6mm ARC. The following is their response: Our BB Neck Sizer die should be very good for Neck sizing only of your new 6 MM ARC cartridges.
Part # BBK2351 comes with three bushings (.260” , .258”, & .256” ).
 
i'm assuming i have a tight chamber and all i really need to do is re-size the neck. Fired case does chamber in the action without any effort. I have reached out to Forester and they said they will get back to me.
For safety and semi auto loading, I always full-length resize semi auto brass (and neck size my bolt gun stuff most of the time). But if your 6 ARC chamber is nice and tight and will consistently feed with neck sizing only, you are in good shape. I bet that thing will shoot bug holes.
 
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Funny you have been using small based dies all this time and didn't know it but you criticize others for buying small base dies.
Anyone can find this info with just a few phone calls. Call every die company and ask to speak to the engineer. Ask them what their target design diameter for the dies are. Yes they all have tolerances and may be a little larger or small but they draw the dies to be made a certain size(target dia). Ben At Hornady has been making custom dies for me 50 at a time for years and Lonnie before him going back 15 years. Either on of those guys can tell you in 2 seconds .004 under minimum chamber size.

Or instead of asking someone else on the phone, get out to the shop and measure what they actually are.

My Hornady 223 dies measure exactly the same at the base as my standard RCBS 223 dies. Not "small base" RCBS dies, but standard. My 6 PPC and Grendel die sets show the same results as well. The actual SMALL BASE dies are the only ones that measure smaller there. (Had to type that in caps so you could figure out which end of the cartridge it refers to.) We are not talking about shoulder diameter here, that is not the issue.

The Hornady dies I have are slightly smaller at the shoulder, but NOT at the base. That doesn't make them small base dies. Are you confused what "small base" means? It sure doesn't have anything to do with the shoulder of fireform rounds.
 
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Can i use a 6mm PPC Neck Sizing Die to resize the 6mm ARC Brass? I have a Uintah Precision Upper on a AR-15 Lower. I have taken the fired brass and head space measures at 1.1910 (SAAMI Spec: 1.1901 - 1.2001) Fired Brass fits in a Wilson 6mm ARC Case Gauge. i'm assuming i have a tight chamber and all i really need to do is re-size the neck. Fired case does chamber in the action without any effort. I have reached out to Forester and they said they will get back to me.

If it's for an AR, you're really going to want a FL die set (and yes, 6PPC dies work great). It doesn't matter if the chamber is "tight" or not; brass and steel stretch under pressure and you're going to need to push some of that brass back for clearance in an autoloader. You might get away with it for one or two reloads, but not much more than that unless you're using really mild loads.
If it's for a bolt action, carry on.