New 6mm Advanced Rifle Cartridge

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.

saami 6.8 barrels are dinosaurs. There is a good reason most are SPCII or ARP, the case and bolt can take more pressure, been proven for a long time.

My point was if they were going to copy a wildcat, why not use a bolt and case that can take pressure.

It's an interesting round that I might invest in, will be watching on the side lines.
 
saami 6.8 barrels are dinosaurs. There is a good reason most are SPCII or ARP, the case and bolt can take more pressure, been proven for a long time.

My point was if they were going to copy a wildcat, why not use a bolt and case that can take pressure.

It's an interesting round that I might invest in, will be watching on the side lines.

The only difference in SPCII is freeboore at .114. You'd still be seating bullets like the 108 ELD-M way down in the case neck to fit mag length, and that's not great. I have serious doubts that Hornady didn't at least consider a smaller case head to gain the durability advantages the bolt would have had - they're just limited in what can be done with magazine length while still using the longer bullets needed for the BCs that make this cartridge make sense. 2600FPS out of an 18" barrel with one of these is going to put you at the 52k region which keeps bolt lugs attached, and gets you out to a thousand yards in most conditions. That's pretty impressive! Case life should be quite good (for an AR15/semi, that is) since these aren't being pushed to crazy pressures.

People are looking at this using interesting lenses, if you're wanting to get that extra 50-100+fps at 60kpsi, you'd be better off moving on to large frame if sticking with AR platform(s). This is a soft recoiling reasonable good-at-most-things cartridge that works with the small frame guns. The tradeoff is lower velocity than you'd get out of a larger cartridge, but I don't think trying to turn an ar15 into a 1500yd+ shooter is prudent either way. Reliability at 52kpsi should be fairly good, you just don't want to load until you start seeing traditional pressure signs like you'd look for on a bolt gun/another cartridge with a more beefy bolt.
 
Yeah I think broken bolts will be an issue for some who look at published load data, then add 2 grains...

The "lawyer" part of the load data is covered in the front of the book where they say it's not their responsibility what you do with the data... not in the reporting of the pressure/velocity vs. charge weight numbers.
 
Yeah I think broken bolts will be an issue for some who look at published load data, then add 2 grains...

The "lawyer" part of the load data is covered in the front of the book where they say it's not their responsibility what you do with the data... not in the reporting of the pressure/velocity vs. charge weight numbers.

I've been guilty myself loading beyond book max in the past with bolt rifles, looking for pressure signs on the cases/primers/etc. The older I get, the more I appreciate more conservative loads, both from a safety perspective as well as from a shooting perspective - the ragged-edge-of-pressure rounds tend to be more finicky and produce less consistent results. I'll give up a few fps to shrink my groups at 1000 any day of the week, it's just hard to get over the HP-wars of velocity when you've not yet had time to learn the advantages of consistency vs. raw velocity.

Flip-side, I sure do wish reloading books would publish pressures on the various loads. Right now the various books are all over the map on 'max loads' and you can't really tell why (conservative numbers or something else) since you don't know what the pressures are. Probably too much to ask in today's lawsuit happy world.
 
1.57 leaves no free bore for 105-110gr projos. And I don't see a big ammo maker (or many AR makers) making the SAAMI MAP 5000psi over the 6.8spc.

ETA: Just seen that CIP has the 6.8 at 58,700psi.
No one is going to run 110s in the ARC either, that bullet is shoved way down in the ARC case too. On top of that all of the Grendel cases are very thin and bulge like a belted magnum when you push pressures. See the photo below from the Grendel forum. To make things worse they decided on a bolt with a .136" recess, that pulls the case .012 further out of the chamber leaving more unsupported by the chamber walls. Look at the sectioned cases and how far down the thin walls of the Grendel case goes compared to the thicker 6.8 case. That should be clear why we can push the 6.8 harder than they can the Grendel cases. I tried to get Starline to make the lower area in the cases thicker only up to the point that the case was supported by the chamber walls but they would not do it...they are in the business of selling brass. Norma brass will outlast all other brands Grendel brass.
The military does not believe in making the freebore .020 in front of the pt of the bullet, all of their freebores are long and have a long jump. The 6mm ARC is a special deal, they even sidestepped the high temperature tests. That is why they had to drop the charges on the 6.8, pressures went through the roof after sitting in a connex in 120* temps all day.
Personally I don't care what the military plays with. Us wildcatters make whatever we want, to do what we want them to.
BTW see the bullet in the Grendel case? That is a 123, now think how long the 110gr is and shorten that Grendel case by .030" The base will be half way to the primer LOL. The 6 ARC will be fine for PRS, hunters and paper punchers but IMO it is the wrong choice for military. mags don't feed that well and AR15 bolts will not hold up especially if they take it to the heat of the sandbox.
grendel belted.jpg

6.8 vs 6.5.jpg
 
Last edited:
  • Like
Reactions: RanchRifle
I don’t see 9310 as that significant of an upgrade to 158. I was thinking more along the lines of more aermet series. I think LMT used to make 7.62x39 bolts out of that.
one on left is like all bolts on the market including JPs, mil spec square lugs. 2nd is superbolt, Titan, 750XD and 800 series. The 800 series was made first(2007) so I could chamber the 6BRX(.473). 750XD(2013) was second (.473, .442, .421 cases), Titan(2015) was the last version because the long ogives of the .224 and 6mm bullets were laying too low in the barrel extension lugs to enter the chamber correctly.
IMG_0370 (2).JPG
 
Grendel/ARC brass can barely hold up to 52000psi. It will be interesting to see what that ammo does in 120* temps.

That's incorrect. I've run the stuff to 60ksi in my Cz. Verified in a SAAMI pressure barrel cut with the same reamer. I have also shot 110's with no real detriment. It's about as heavy as a guy would ever want to go for the case capacity, but far from being unreasonable. Better than trying to push 130gr class pills in the Grendel.

We've talked about that picture before (belts). IIRC you never physically handled the particular barrel and by pixel-estimating lengths I'm fairly certain there was a machining goof to produce those belts.


110 in the ARC @ AR15 mag length:
KIMG1829.JPG


I've got the benefit of having a 2.33" or so magazine in the CZ. Anyone running it in an AICS kit/mag will have 2.50.
 
one on left is like all bolts on the market including JPs, mil spec square lugs. 2nd is superbolt, Titan, 750XD and 800 series. The 800 series was made first(2007) so I could chamber the 6BRX(.473). 750XD(2013) was second (.473, .442, .421 cases), Titan(2015) was the last version because the long ogives of the .224 and 6mm bullets were laying too low in the barrel extension lugs to enter the chamber correctly.
View attachment 7347814
Nice! Did not know these existed. I assume you have to use a proprietary extension? Similar to the KAC E3 bolt?
 
That's incorrect. I've run the stuff to 60ksi in my Cz. Verified in a SAAMI pressure barrel cut with the same reamer. I have also shot 110's with no real detriment. It's about as heavy as a guy would ever want to go for the case capacity, but far from being unreasonable. Better than trying to push 130gr class pills in the Grendel.

We've talked about that picture before (belts). IIRC you never physically handled the particular barrel and by pixel-estimating lengths I'm fairly certain there was a machining goof to produce those belts.


110 in the ARC @ AR15 mag length:
View attachment 7347819

I've got the benefit of having a 2.33" or so magazine in the CZ. Anyone running it in an AICS kit/mag will have 2.50.
And here I thought we were talking about this 6mm ARC in AR15s, who knew?
 
  • Like
Reactions: RanchRifle
Nice! Did not know these existed. I assume you have to use a proprietary extension? Similar to the KAC E3 bolt?
Yes, The 800 series and 750 XD used the same extension but the newer Titan extension is different. The 750xd and 800 series bolts are a lot larger than the KAC. I would guess the Titan bolt is .010 larger in major diameter than the KAC.
 
  • Like
Reactions: RanchRifle
And here I thought we were talking about this 6mm ARC in AR15s, who knew?

You said the brass can't handle 60ksi. It can. The AR-15 shouldn't be eating 60ksi grendel/ARC loads so IMO it's a moot point that when/if you load them up to 60-70ksi they fail in an AR-15. Properly supported it's just like any other case. I don't have any of the barrels that fired any of the cases in those pictures, but I'd be happy to entertain the breech/extension/bolt measurements on any of them if you have them.

I'll admit I haven't followed the 6.5 Grendel very closely in the last 5-6 years, but I was into it from ~2007-2015 and most every case of a broken bolt or brass issue was from someone hand loading with no indication of what pressure they were loading to, trying to get as much speed as they could. And let me be clear, nobody is suggesting that you can load the ARC or the grendel to 60ksi in an AR-15.

ALL of the published data is from 52ksi loads, 7mmShooter, and the factory ammo (52ksi) matches the published charts/numbers for MV.
 
You said the brass can't handle 60ksi. It can. The AR-15 shouldn't be eating 60ksi grendel/ARC loads so IMO it's a moot point that when/if you load them up to 60-70ksi they fail in an AR-15. Properly supported it's just like any other case. I don't have any of the barrels that fired any of the cases in those pictures, but I'd be happy to entertain the breech/extension/bolt measurements on any of them if you have them.

I'll admit I haven't followed the 6.5 Grendel very closely in the last 5-6 years, but I was into it from ~2007-2015 and most every case of a broken bolt or brass issue was from someone hand loading with no indication of what pressure they were loading to, trying to get as much speed as they could. And let me be clear, nobody is suggesting that you can load the ARC or the grendel to 60ksi in an AR-15.

ALL of the published data is from 52ksi loads, 7mmShooter, and the factory ammo (52ksi) matches the published charts/numbers for MV.
Thanks LedZep, that's where I got confused. I figured it was from 52k yet you mentioned 60k a while back but I see that was for a bolt gun. That clears up my questions and puts things back on track a bit. Hey H, your ARC barrels will be coming set up to a Titan bolt correct?
 
Thanks LedZep, that's where I got confused. I figured it was from 52k yet you mentioned 60k a while back. That clears up my questions and puts things back on track a bit. Hey H, your ARC barrels will be coming set up to a Titan bolt correct?
The Titan bolts have a .124 recess. I designed the extension so a normal mil spec bolt could be used with them if it was an emergency , so that means a 7.62x39 bolt. You can see how that may be a problem with all other ARC barrels using a .136 recess type 2 bolt. I'm sorry I have no idea what I'll do yet. I've been making 6mmARs/243LBCs/6mm Predators and Banshees since 2007 and now we have something just a little different.
 
The Titan bolts have a .124 recess. I designed the extension so a normal mil spec bolt could be used with them if it was an emergency , so that means a 7.62x39 bolt. You can see how that may be a problem with all other ARC barrels using a .136 recess type 2 bolt. I'm sorry I have no idea what I'll do yet. I've been making 6mmARs/243LBCs/6mm Predators and Banshees since 2007 and now we have something just a little different.
No sweat, it came back to me a couple minutes ago of the recess difference between the two but you had already replied before I could edit my post. Multiple ways to skin a cat
 
What do you mean by "failed to work"? I've got die sets from several manufacturers including Hornady and while some are nicer than others they all "work".
 
What do you mean by "failed to work"? I've got die sets from several manufacturers including Hornady and while some are nicer than others they all "work".


Getting to desired bump and thier factory crimp to work, etc.
Been a while since I ran one.
Won't happen again.

I have some Hornady tools and bullets I use.

Glad someone gets use of thier dies but I would give them 2 thumbs down.
And that is not comparing them to what are considered premium brands.

7 different calibers for 5 shooters and one brand that didn't cut it.
That is all I have to base my opinion on at this point.

They didn't work.
 
No one is going to run 110s in the ARC either, that bullet is shoved way down in the ARC case too. On top of that all of the Grendel cases are very thin and bulge like a belted magnum when you push pressures. See the photo below from the Grendel forum. To make things worse they decided on a bolt with a .136" recess, that pulls the case .012 further out of the chamber leaving more unsupported by the chamber walls. Look at the sectioned cases and how far down the thin walls of the Grendel case goes compared to the thicker 6.8 case. That should be clear why we can push the 6.8 harder than they can the Grendel cases. I tried to get Starline to make the lower area in the cases thicker only up to the point that the case was supported by the chamber walls but they would not do it...they are in the business of selling brass. Norma brass will outlast all other brands Grendel brass.
The military does not believe in making the freebore .020 in front of the pt of the bullet, all of their freebores are long and have a long jump. The 6mm ARC is a special deal, they even sidestepped the high temperature tests. That is why they had to drop the charges on the 6.8, pressures went through the roof after sitting in a connex in 120* temps all day.
Personally I don't care what the military plays with. Us wildcatters make whatever we want, to do what we want them to.
BTW see the bullet in the Grendel case? That is a 123, now think how long the 110gr is and shorten that Grendel case by .030" The base will be half way to the primer LOL. The 6 ARC will be fine for PRS, hunters and paper punchers but IMO it is the wrong choice for military. mags don't feed that well and AR15 bolts will not hold up especially if they take it to the heat of the sandbox.
View attachment 7347794
View attachment 7347795

I don't really get why you're here talking down the new round, up until very recently you had a paragraph on your website saying that you would be selling 6mm ARC barrels and to check back in late summer or something like that. I don't see it on there anymore, are you no longer planning on selling 6mm ARC barrels?

I think every time I've seen those "belted" Grendel case photos posted somewhere, it's always you whose posted them. No one I've ever shot with, or even talked to has actually had that problem, I assume it's from loading way, way over pressure?

Is your signature line on 68forums still something to the effect of "Proud to have done more than any other person to damage the 6.5 Grendel"? I have one Grendel that I've shot some and like alright, I'm not head over heels for it but I certainly don't understand the point of holding an animosity towards a chambering.
 
Last edited:
Getting to desired bump and thier factory crimp to work, etc.
Been a while since I ran one.
Won't happen again.

I have some Hornady tools and bullets I use.

Glad someone gets use of thier dies but I would give them 2 thumbs down.
And that is not comparing them to what are considered premium brands.

7 different calibers for 5 shooters and one brand that didn't cut it.
That is all I have to base my opinion on at this point.

They didn't work.

Well if you couldn't get Hornady dies to work for you, it's good that you found something else.
 
Troll someone more your size.

First off, I don't know what that's supposed to mean, are you bigger or smaller than me? Second, I'm not trolling, let me put it plainly, If you couldn't get multiple sets of Hornady dies to work, you were either screwing up or you're the world's unluckiest guy and you should have been sending all those out of spec dies back to be fixed on Hornady's dime. I know which one my money is on, but if you dumped them and found excellence with Lee, good for you. (y)
 
Last edited:
I don't really get why you're here talking down the new round, up until very recently you had a paragraph on your website saying that you would be selling 6mm ARC barrels and to check back in late summer or something like that. I don't see it on there anymore, are you no longer planning on selling 6mm ARC barrels?

I think every time I've seen those "belted" Grendel case photos posted somewhere, it's always you whose posted them. No one I've ever shot with, or even talked to has actually had that problem, I assume it's from loading way, way over pressure?

Is your signature line on 68forums still something to the effect of "Proud to have done more than any other person to damage the 6.5 Grendel"? I have one Grendel that I've shot some and like alright, I'm not head over heels for it but I certainly don't understand the point of holding an animosity towards a chambering.

He never got over that time his wife told him she preferred Bill Alexander's longer bullet with its superior ballistic coefficient. His shorter, slightly thicker 6.8 might have been okay for the first bit, but over distance Alexander's bc really outperformed.
 
Hmmm....Brady here has shot both box ammo and his hand loads. His hand loads the brass already has been reloaded a couple of times. No problems with a belt/case head being blown out like in the pictures shown earlier in the thread.

He's also stepping on it a bit I will say as well. 105gr bullets going 2885fps out of a 24" barrel gas gun. Thing just shoots tiny small groups. He will be shooting it more this coming weekend.

Later, Frank
Bartlein Barrels
 
Hmmm....Brady here has shot both box ammo and his hand loads. His hand loads the brass already has been reloaded a couple of times. No problems with a belt/case head being blown out like in the pictures shown earlier in the thread.

He's also stepping on it a bit I will say as well. 105gr bullets going 2885fps out of a 24" barrel gas gun. Thing just shoots tiny small groups. He will be shooting it more this coming weekend.

Later, Frank
Bartlein Barrels
Who do I call to order a barrel? 😁
 
Yeah all of Hornadys dies are made .004 under minimum chamber size so they are all really small base dies whether they say it or not.
Does it appear the belts are being caused by the dies or by firing where that portion of the case is unsupported?

After a few firings of Hornady brass, I'm getting a smidge of that belt on my cases. I don't remember seeing it when I ran AA and Lapua brass (same thing I know). But, that was a different rifle too. It was a Satern barrel/extension and bolt.

Added: Hornady Dies
Not all of Hornady dies are my favorites. I will never use their "American" series again. They are extremely small base. There is no way to simply neck-size with them as when you come far enough down the neck, you are sizing down the middle of the case. The "New dimension" have been mostly hit with a couple misses. One in particular everyone missed, except Redding, and that is the Swiss 7.5X55 for the K-31.

In all honesty, I'm not overly fond of Lee either. For each loading session at the bench, I do alright. But, the rubber o-ring and loose lock fit, tend to make each session just a little different on each cartridge. I never use them for precision loading. The majority of my dies are RCBS. Which is good for most of what I do and more consistent between loadings of each different cartridge I load for. Redding, Wilson and Forster are my precision dies.
 
Last edited:
  • Like
Reactions: Snuby642
I don't really get why you're here talking down the new round, up until very recently you had a paragraph on your website saying that you would be selling 6mm ARC barrels and to check back in late summer or something like that. I don't see it on there anymore, are you no longer planning on selling 6mm ARC barrels?

I think every time I've seen those "belted" Grendel case photos posted somewhere, it's always you whose posted them. No one I've ever shot with, or even talked to has actually had that problem, I assume it's from loading way, way over pressure?

Is your signature line on 68forums still something to the effect of "Proud to have done more than any other person to damage the 6.5 Grendel"? I have one Grendel that I've shot some and like alright, I'm not head over heels for it but I certainly don't understand the point of holding an animosity towards a chambering.
At the moment I am swamped with other orders, I don't have a production spot open for them. I do not know if I will produce barrels or not since I have stopped machining Grendel bolts and would need to buy them from someone.
It's called facts. I've been shooting a Grendel since 2005, actually it was called a 6.5CSS back then. I've been making 6mm Grendels for lack of a better term since 2007, 224 Grendels also. Like I said above it works fine and is accurate for target, varmint and PRS but IMO it is not a good choice for the military in a AR15 rifle because of the bolt and mag problems. IF you push the pressure the case will swell into the chamfer at the breech, you should be able to look at the photos above and see that. The section view should show very clearly why the cases swell especially when the .136 bolt face pulls the case .012" further out of the chamber exposing even more thin wall.
As for the digs on the Grendel Horde, they have been posting so much BS since 2006 that I say stuff just to piss them off. The photos posted above come from the Grendel forum if Hanka hasn't removed them along with all the broken bolt threads.
 
  • Like
Reactions: RanchRifle
Does it appear the belts are being caused by the dies or by firing where that portion of the case is unsupported?

After a few firings of Hornady brass, I'm getting a smidge of that belt on my cases. I don't remember seeing it when I ran AA and Lapua brass (same thing I know). But, that was a different rifle too. It was a Satern barrel/extension and bolt.
It is caused by being unsupported, the chamfer at the breech. Since 2007 the 6mm stuffed in a Grendel case has always been a wildcat, there were no loads printed so we had to work up loads and in doing that some are going to be high pressure I mean you don't know what is high pressure until you get there. Most other cases, 5.56, 308 etc will show flat primers first or ejector swipes but with these thin cases you may get that belt or even a rupture before the primers flatten and flat primers is usually the big sign to back off. I've been a wildcatter since 1982 and in all of those years I have only had 4 case rupture when developing loads, 2 of those were from a 6mm in a Grendel case in an AR. The first was using H4895 with a 95gr SMK bullet. Now that this thing has been SAAMIed and there will be many more people working up loads there will be many more belted magnum photos popping up. I suggest measuring the diameter of the bases just above the groove as a pressure indicator instead of waiting for the primers to show signs.
 
Here's the loosest in-spec fit you can get.

The vertical line is where the belt is showing on the cases pictured above based on pixel count vs. 'known' diameter. I tend to think the breech face or chamfer is generous on the barrels producing that. Even when I was blowing primers on the Wolf Gold grendel brass (large rifle pocket) I never got a belt. That brass was the thinnest softest crap ever.

It's whatever. Obviously it happened, but I don't think it's fair to say it's a systemic issue with PPC-based cartridges. I'm more inclined to believe it's a manufacturing error on the barrel side. Again, without knowing what the dimensions are of the parts that produced that, the pictures are near meaningless as far as determining the root cause. If you posted pictures like that of 5.56 brass (I've seen those, too) I suspect the immediate response would be "Out of spec barrel".


gbelt.JPG
 
At the moment I am swamped with other orders, I don't have a production spot open for them. I do not know if I will produce barrels or not since I have stopped machining Grendel bolts and would need to buy them from someone.
It's called facts. I've been shooting a Grendel since 2005, actually it was called a 6.5CSS back then. I've been making 6mm Grendels for lack of a better term since 2007, 224 Grendels also. Like I said above it works fine and is accurate for target, varmint and PRS but IMO it is not a good choice for the military in a AR15 rifle because of the bolt and mag problems. IF you push the pressure the case will swell into the chamfer at the breech, you should be able to look at the photos above and see that. The section view should show very clearly why the cases swell especially when the .136 bolt face pulls the case .012" further out of the chamber exposing even more thin wall.
As for the digs on the Grendel Horde, they have been posting so much BS since 2006 that I say stuff just to piss them off. The photos posted above come from the Grendel forum if Hanka hasn't removed them along with all the broken bolt threads.
I've had a lot of frustrations over the years with Grendels. Part of it seems that no Grendel rifle had been gone through and matched machine-wise to the loads, capabilities, and choosing one criteria over the other that limits performance. If it was set for one load, it would be easier. I've come to find, you get what you get, and it's generally not velocity, for the whole rifle as a system to work. But, I have really liked my Grendels. Although, looking back, I wished I had gone with 6mm.

That said, I agree there has been truckloads of BS about what the Grendel is. Which has spawned "alternate-Grendel" people to spew on it. It is a medium cartridge with potential with high BC rounds. It actually does quite well with not-too-limited range light bullets. I think it has a ton of military potential. But, several key facets have to be addressed. First and foremost being not everyone needs a sniper round for average military use. A lighter faster bullet will reach pretty far out there. And, have better terminal ballistics at closer ranges, as well as twice the terminal ballistics of the current 62. gr. in .224"
 
Here's the loosest in-spec fit you can get.

The vertical line is where the belt is showing on the cases pictured above based on pixel count vs. 'known' diameter. I tend to think the breech face or chamfer is generous on the barrels producing that. Even when I was blowing primers on the Wolf Gold grendel brass (large rifle pocket) I never got a belt. That brass was the thinnest softest crap ever.

It's whatever. Obviously it happened, but I don't think it's fair to say it's a systemic issue with PPC-based cartridges. I'm more inclined to believe it's a manufacturing error on the barrel side. Again, without knowing what the dimensions are of the parts that produced that, the pictures are near meaningless as far as determining the root cause. If you posted pictures like that of 5.56 brass (I've seen those, too) I suspect the immediate response would be "Out of spec barrel".


View attachment 7348003
you know the rim on a Grendel case is around .050 thick right? And you drew the chamfer how big? Some barrels makers use a flat angle like you have drawn but better companies use a radius chamfer. I think if you ever get you hands on an AR barrel and measure the chamfer you will see that most are not what you think they are. Bolt guns don't need much of a chamfer.

Next instead of guessing why don't you section a Grendel case and measure the thickness of the brass in that area and then do the same with a 5.56, 308 and 6.8 related to the base of the case . The section photo above is pretty clear but I don't think you will understand until you measure it yourself.

Some of you seem a little sensitive about things I have said so IMO the 6mm version of the Grendel 6mm ARC or whatever is one of the best cartridges for AR15s for hunting varmints, long range shooting and PRS. IF Hornady makes their brass thicker at the bottom it could solve the bulging problems, If someone made a bigger stronger bolt they may last longer. If someone made a bigger magwel Magpul could make mags that would work with .442 diameter cases without modification. Get all that done and it would be perfect.
 
Last edited:
  • Like
Reactions: RanchRifle and KaM
That's pretty darn close to Dasher velocity.

I'm going to tell you that it is bascially Dasher velocities.

My 27.25 Dasher barrel with H4350 I was just over 2900fps. Can you get more out of the Dasher? Sure but I will say this.

The load I ran thru my gun was also a load run thru a pressure test barrel. The pressure test barrel was one we made for a powder maker and was a 1-8 twist and 30" finish and the same load as mine it was only 16fps faster out of the 30" barrel. My load was at normal max working pressure. I could get more out of it but I would be technically be over max working pressure.

So I'll tell you guys are running the Dasher faster/hotter and don't really know they are over the max working pressure for the round at times. Just like everything else.

I haven't seen data for Brady's load out of a pressure test barrel and like I said he is stepping on it a some. If I had to put honest numbers on it I'd say in the day in and day our real world pressures/velocities the Dasher is probably 50-75fps faster and that's it.
 
  • Like
Reactions: long range sponge
Gotta love all the broken bolt talk when a grendel is brought up. Here's a novel idea, stop being so poor and spend an extra $75 and buy a spare bolt. They rarely ever break these days. And for God sakes if you're worried about getting belts on your cases, it means YOU made the ammo too hot, not that it's some sort of design flaw.
 
Have you ever noticed the chamfer at the breech of all AR15 barrels? Did this guy have a goof?
View attachment 7347826
What about this guy?
View attachment 7347827

Like I've mentioned before when you posted these pics in previous 6mmGR threads, I've never had that bulging happen before??!!

That's after putting 1500 rounds of various loads in a 6mmART40 and 800-ish in a 6mmFatRat. My loads were/are, not light, I'd consider them medium heavy.

I don't know which bolt Whitley or Lee Wells used.

My Lapua cases have a slight ejector smear and primers are starting to get flat and velocities are/were, high. 2870 fps in a 22" Wilson 8 twist with 95 SMK in the FatRat and was in the same FPS region with 105 Amax in the 26" 8 twist 6mmART40.

There's no trick or magic to it, just don't push the pressures beyond what the "system" allows.

Oh, and both of these have the +2" gas port so that may be why I haven't had any problems???

Also I learned to stay with H-4895 which is temp stable.
 
you know the rim on a Grendel case is around .050 thick right? And you drew the chamfer how big? Some barrels makers use a flat angle like you have drawn but better companies use a radius chamfer. I think if you ever get you hands on an AR barrel and measure the chamfer you will see that most are not what you think they are. Bolt guns don't need much of a chamfer.

Next instead of guessing why don't you section a Grendel case and measure the thickness of the brass in that area and then do the same with a 5.56, 308 and 6.8 related to the base of the case . The section photo above is pretty clear but I don't think you will understand until you measure it yourself.

Some of you seem a little sensitive about things I have said so IMO the 6mm version of the Grendel 6mm ARC or whatever is one of the best cartridges for AR15s for hunting varmints, long range shooting and PRS. IF Hornady makes their brass thicker at the bottom it could solve the bulging problems, If someone made a bigger stronger bolt they may last longer. If someone made a bigger magwel Magpul could make mags that would work with .442 diameter cases without modification. Get all that done and it would be perfect.

Case dimensions are to SAAMI spec. I hit the middle of the spec for rim thickness, .054". Chamfer is .550" major diameter @ 120 degree included angle. Regardless, even if I blow that major diameter out to .615 to account for the same width of chamfer (looking from the back) as a 5.56 a guy would have to push the breech face forward .025-.045 to get the chamfer intersection with the chamber in the same place as those belts in your pictures. Essentially .035-.055 clearance in front of the bolt, OR a .100" radius, or

Cross section is .039 vs. .047, 6 ARC vs. .308 on web thickness before the radius transition. Height is .205 (arc) vs. .215 (.308) head to the point that would fail.
ARCv308.JPG


gbelt2.JPG


I'm over this conversation. The chamfer/radius geometry and bolt nose clearances are EASY to make work with this case. If you cut the tennon an extra .025-050 short before screwing the extension on that's not the case's problem. I've seen AR-15's on the internet in 5.56 with the issue, and I know someone personally that fucked up the chamfer on an AR-10 .308 barrel and the resulting belts and/or blow-outs were not the cases' fault. No different with the Grendel/ARC.
 
Gotta love all the broken bolt talk when a grendel is brought up. Here's a novel idea, stop being so poor and spend an extra $75 and buy a spare bolt. They rarely ever break these days. And for God sakes if you're worried about getting belts on your cases, it means YOU made the ammo too hot, not that it's some sort of design flaw.
You'll have to go find those 4 threads and tell those 4 guys why their cases are swelled, they sounded pretty worried.
 
  • Like
Reactions: RanchRifle
It is caused by being unsupported, the chamfer at the breech. Since 2007 the 6mm stuffed in a Grendel case has always been a wildcat, there were no loads printed so we had to work up loads and in doing that some are going to be high pressure I mean you don't know what is high pressure until you get there. Most other cases, 5.56, 308 etc will show flat primers first or ejector swipes but with these thin cases you may get that belt or even a rupture before the primers flatten and flat primers is usually the big sign to back off. I've been a wildcatter since 1982 and in all of those years I have only had 4 case rupture when developing loads, 2 of those were from a 6mm in a Grendel case in an AR. The first was using H4895 with a 95gr SMK bullet. Now that this thing has been SAAMIed and there will be many more people working up loads there will be many more belted magnum photos popping up. I suggest measuring the diameter of the bases just above the groove as a pressure indicator instead of waiting for the primers to show signs.

I played with the Grendel for 5 or 6 years and only had belted cases one time. I got my suppressor out of jail and shot my XBR8208 load and had the belted magnum look. Add an adjustable gas block and a heavier buffer and the problem disappeared. Found I liked shooting my 260 and 6.5 Creedmoor bolt guns more than the Grendel, so I sold it, all my brass, and reloading stuff for it. Always thought a 6mm or 224 Grendel would made a good hunting rifle, now that there is a factory option, I may try it.
 
Always thought it was interesting Wolf sold Grendel ammo. What are the chances they start with ARC ammo?

I know it's just blasting ammo, but at 30 cents a round, a Grendel is awfully close to 223 costs. Still not sure where I stand on the bimetal jacket discussion but I've stayed away so far