6br in an AR rifle

[69mach]

Something to consider...As case diameter increases, so does bolt thrust, which is the weak link in the ar15 platform. I doubt you'd realize any benefit of the br case over the Grendel case in that platform, and as others have alluded to, the bugs are worked out beforehand. I suggest reconsidering a Grendel variant, but that's just me. If you look at saami max pressures for a 5.56 vs a Grendel, then run the bolt thrust numbers, the max pressures of the Grendel are proportionately less..in this platform and because of it. In a bolt gun, it is a different story. That's why some manuals offer service rifle load data as well as bolt gun data. I don't know if you'll find both data for the Grendel at this time. At least, I don't remember seeing bolt gun data for it. Regardless, with the larger case head area of the br, it WILL create more bolt thrust and thus lower max pressures. If you go ar10, disregard all of this.

I shoot a 6 and a 30 cal based on the Grendel in bolt action BR rifles and couldn't be any happier with the case, all the way around. It's a fantastic cartridge to work with, particularly so with Lapua brass. I just don't think you'll see any benefit of the slight capacity increase of the br case over the grendel. I'd lean toward a straight grendel case but an improved variant is certainly a viable option. Just my 2 cents worth on the subject. Before someone says the improved Grendel bolts will fix it...trust me, I've broken them too! They are better but are still the weakest link in the system and are not a panacea that will allow bolt action pressures from an ar15 rifle. Going to a br case will just compound the issue further, even if you were to use a grendel bolt with rebated rimmed br cases.

A member pmed me about a B.R.A.T built 6brx he has that he would sell. It looks interesting to me and I’d like to try it out. He said it shoots well and I have no doubt it does. I’ve read about brat before but can’t find a website for them. Are they in business anymore? He sent me some info on it and it looks like they use a much larger proprietary bolt. It looks like a well built bolt. Anyone have experience with b.r.a.t. ?

 

[gunsandgunsmithing]

A member pmed me about a B.R.A.T built 6brx he has that he would sell. It looks interesting to me and I’d like to try it out. He said it shoots well and I have no doubt it does. I’ve read about brat before but can’t find a website for them. Are they in business anymore? He sent me some info on it and it looks like they use a much larger proprietary bolt. It looks like a well built bolt. Anyone have experience with b.r.a.t. ?

I can't be of much help in regard to them. I was aware but have no firsthand experience with them. I would like to get one in my hands to look over. There simply isn't much room to go much bigger with the bolt and/or barrel extension. The extension is only about .060" thick IIRC, with a std bolt and the upper doesn't have much room to go with a bigger extension...So, I would like to know how they are getting there.

It looks to be an AR10 bolt, or close, in which case I think the bolt would be fine. That brings the thickness of the extension into question and the strength of the upper where the larger extension must be. IMHO, that area is already too thin to support much of a bbl out there. Maybe they're doing something else, but on the surface, I don't see how they aren't giving up something, somewhere. If it works, it works. If you can load the br and grendel cases, both to full on max, there still isn't much difference though. The improved grendel, such as a 6Rat puts you pretty much on par with the br with less bolt thrust. If the bolt holds up and there are no other significant trade offs elsewhere, you would see some gain with a BRX, BRDX, Dasher, etc. It really is up to you to find out if there are any negatives for using the brat upper for your intended use, and go from there. They somehow do "modify" the upper to use a bigger bbl extension. If that means..and it likely does, that the upper is thinned for a larger bbl extension...it would be a concern to me, for best accuracy. I read somewhere that they only have 5 round mags. Not sure if that's true or not and how reliably they function.

If you go that route, I'd like to hear your feedback.--Mike

 

[10at6]

I can't be of much help in regard to them. I was aware but have no firsthand experience with them. I would like to get one in my hands to look over. There simply isn't much room to go much bigger with the bolt and/or barrel extension. The extension is only about .060" thick IIRC, with a std bolt and the upper doesn't have much room to go with a bigger extension...So, I would like to know how they are getting there.

It looks to be an AR10 bolt, or close, in which case I think the bolt would be fine. That brings the thickness of the extension into question and the strength of the upper where the larger extension must be. IMHO, that area is already too thin to support much of a bbl out there. Maybe they're doing something else, but on the surface, I don't see how they aren't giving up something, somewhere. If it works, it works. If you can load the br and grendel cases, both to full on max, there still isn't much difference though. The improved grendel, such as a 6Rat puts you pretty much on par with the br with less bolt thrust. If the bolt holds up and there are no other significant trade offs elsewhere, you would see some gain with a BRX, BRDX, Dasher, etc. It really is up to you to find out if there are any negatives for using the brat upper for your intended use, and go from there. They somehow do "modify" the upper to use a bigger bbl extension. If that means..and it likely does, that the upper is thinned for a larger bbl extension...it would be a concern to me, for best accuracy. I read somewhere that they only have 5 round mags. Not sure if that's true or not and how reliably they function.

If you go that route, I'd like to hear your feedback.--Mike

Friend had one and it worked OK but he had some trouble feeding if I recall .I believe the quit making that bolt and extension for a reason. You are pushing the envelope for sure. I have a 6 rat and that's all I would want in a 15 frame rifle
The regular 6 AR is what I would do if I could do it over. Rat and turbo are basically the same thing

 

[maxscm]

Another Option in the AR15 format is 6mm x 6.8 SPC.
I have one But its strictly a Coyote Buster, with A 16 inch BHW Barrel, Suppressed.
shoots good tooo!

 

[mensajd]

Some vendors are using much larger bolts and commensurately beefier barrel extensions and upper receivers for their nonstandard ar-15 caliber uppers.

 

[CT10ring]

Don't overthink this.

6mmAR. 22-26" tube. Work's already been done.

Readymade at SABRECO.

there you go. Fred S does excellent work. Super

I talked to fred at sabreco I left a message and he called me back the next day and was very nice and helpful. Off topic the only other guy that was this helpful that ive talked to was bob white. Fred made a good case for the 6mm turbo 40. He said that it is what he would get for bench shooting. He said alot of his rifles maintain a 1/4 minute but I'd have to order through 6mmar.com since it was their proprietary cartridge, he just does the Smith work for them.

6AR is a great cartridge. I had upper built by Fred ( super job) & it was indeed 1/4 min. - I used for varminting. Sold it years back-mistake.
I used all of the 6mAR load data & it was spot on. forming brass is easy. fwiw...

 

[69mach]

Some vendors are using much larger bolts and commensurately beefier barrel extensions and upper receivers for their nonstandard ar-15 caliber uppers.

Yea dedicated technology does a lot with the wssm cases. For the money I think id prefer a premium cut rifled barrel such as a krieger or bartlien not that dtech s shilen match and select match barrel won't shoot lights out, I've just personally had sour luck with shillen

 

[1shot]

6mmAR which is a 6mm Grendel. Shoot a 95 grain match bullet in a 8 inch twist and you’re golden.

My ATC rifle is in 6AR. 90 gr. for the short line and 105’s at 600. Just put a new Bartlien 5R bbl. on it and has been sitting in the vault collecting dust ever since. A true tack driver with nary a malfunction. You might want to take a hard look at those choices.
I hope this helps,
Lloyd

 

[69mach]

My ATC rifle is in 6AR. 90 gr. for the short line and 105’s at 600. Just put a new bbl. on it and has been sitting in the vault collecting dust ever since. A true tack driver with nary a malfunction. You might want to take a hard look at those choices.
I hope this helps,
Lloyd

I've read on the 6ar the 6mm predator the 6 turbo, the 6turbo 40, 6rat 6fatrat the spc cases the 6 woa the 6 haggar, 6dti and some others I I've forgot now. I wish someone on here would keep a page going with the br family of cases the Grendel family of cases and the spc family of cases and put the pertinent info of each cartridge. It's hard to keep up with what's what lol

 

[Ga-Bulldog]

gunsandgunsmithing hit all the points perfectly. Just buy your choice of Grendel based upper. Fred does great work.

I have a 6BR in an AR and I had a 6mmAR. I first bought the 6AR and then had the opportunity to buy the 6BR. My BR uses a PPC bolt and came with 700 pieces of new rebated rim lapua brass so it's been super easy for me to shoot. It does not shoot any better than the 6AR turbo I had for a couple of years. Only reason I sold the 6AR was because I also had a 6br bolt gun.
I never saw the need to push a 105gr much past 2800fps, just like the 6AR will do. I only use mine for NRA XTC matches and there is no real gain on a 600 yard target, no matter what it will use more windage than a 6XC. I think I have about 1500 rounds through it, no problems using the PRI 6.8 mags.

 

[Ga-Bulldog]

Guys, do any of you know if the 6mmAR guys are still in business? I have been trying to get in touch to purchase a upper 6mmAR Turbo but have had no luck. Thanks in advance for your help, gary

 

[Dusty Stevens]

Theres plenty of other choices if you can go with a comparable cartridge by a different name

 

[nmjwolf]

https://accurateandreliablerifle.com/

Lee's great to deal with.

 

[arnie]

How would the bolt face be to big for a br case? I’d think an ar10 308 bolt would work fine. I figured it was more of a problem with feeding and cycling reliably.

We were talking ar15 not ar10

 

[69mach]

We were talking ar15 not ar10

The post question asked about both AR15 and ar10s. Also I don’t know why a 6br case head is to big. Doesn’t a 458 socom use the same bolt? It’s chambered in AR15 platform rifles

 

[Bamban]

Resurrecting an old thread..

So, what is the verdict?

458 SOCOM use .473 bolt face, and case body dimensions are not that far apart. The big difference I can see, the big bore AR15s are low pressure rounds, maybe under 40K, whereas the others in discussion (6BR and derivatives) could be 30 to 40% more pressure. Maybe using the Whiteoak competition barrel extension with 13/16x20 TPI and .300 longer than standard barrel extension might help a little in the 3 rings of metal surrounding the case.

https://www.whiteoakarmament.com/sh...el-group/competition-barrel-extension-m4.html

I was about to repurpose a takeoff benchrest barrel in 6 PPC into Norma 6 Dasher and shoot 68 grain bullets when I ran into this old thread. I am interested in inputs.

 

[Laurie]

In a bolt gun, it is a different story. That's why some manuals offer service rifle load data as well as bolt gun data. I don't know if you'll find both data for the Grendel at this time. At least, I don't remember seeing bolt gun data for it. Regardless, with the larger case head area of the br, it WILL create more bolt thrust and thus lower max pressures. If you go ar10, disregard all of this.

I've been looking for any Grendel data I can find (with a Mini 1500 in mind) and no, it seems to be all AR pressure based. Thank you for the explanation as I'd been much puzzled about a reason for the Grendel's apparently low SAAMI/CIP MAP values. I'd clean forgotten about thrust rising alongside case-head diameter.

 

[10at6]

I think a 6AR is a might be a better choice in an AR15 and much easier if the chamber will clean up.
Good luck. Sounds like a great varmint rifle.
The problem with the BR based cases was bolt thrust from what I know

 

[riflewoman]

I've been looking for any Grendel data I can find (with a Mini 1500 in mind) and no, it seems to be all AR pressure based. Thank you for the explanation as I'd been much puzzled about a reason for the Grendel's apparently low SAAMI/CIP MAP values. I'd clean forgotten about thrust rising alongside case-head diameter.

Try http://www.6mmar.com/6mm_AR_Loading_Info.html.

You might be able to go up as much as a grain but it will depend on your individual rifle FAR more than your action type. Nothing wrong with the loads as written by the way. A lot of AR shooters seem to be happier with the 95 grain bullets.