6BR AR Upper
- Thread starter joghotrod
- Start date
From what I've heard the reason there aren't more 6BR uppers for the AR is one of liability: there's so little metal left around a 6BR chamber in an AR barrel it's a risky proposition.
That's not to say you can't build and shoot one, but keep in mind what you're handling when working up loads.
John Harrison's 6HAGAR - based on the .30 Remington case - has almost exactly the same case capacity once once-fired; next is Robert Whitley's 6mmAR,necked-down 6.5 Grendel case), then comes John Holliger's 6WOA,necked-down 6.8 SPC case).
The folks who brought us the Tubb 2000 bolt rifle stopped offering 6BR for a factory chambering option a few years back due to a number of case failures.
That's not to say you can't build and shoot one, but keep in mind what you're handling when working up loads.
John Harrison's 6HAGAR - based on the .30 Remington case - has almost exactly the same case capacity once once-fired; next is Robert Whitley's 6mmAR,necked-down 6.5 Grendel case), then comes John Holliger's 6WOA,necked-down 6.8 SPC case).
The folks who brought us the Tubb 2000 bolt rifle stopped offering 6BR for a factory chambering option a few years back due to a number of case failures.
For the T2k I think it was unsupported case area that gave rise to the failure rate, coupled with the tendency to load the 6BR pretty hot.
As for the 6BR in an AR: I'll try to locate the threads on other forums I follow.
Inquire of Anna Kinney via e-mail at http://www.first-strike-products.com/
I know she's a lot more experienced with 6BR on the AR platform than I am, and a heck of a fine competitive high power shooter as well.
As for the 6BR in an AR: I'll try to locate the threads on other forums I follow.
Inquire of Anna Kinney via e-mail at http://www.first-strike-products.com/
I know she's a lot more experienced with 6BR on the AR platform than I am, and a heck of a fine competitive high power shooter as well.
spclark said:
I think joghotrod is correct. The WSSM has a larger chamber, and runs at a higher pressure than the BR an we haven't had ANY problems with brass or the chamber. In fact, back when we were doing destructive testing on the WSSM system, we couldn't get enough fast burning rifle powder in the case to do anything but ruin cases. Finally we put 26 grains of bulls-eye behind a 100 grain .243 bullet and pulled the cord. The bottom of the carrier blew down through the mag-well, but the barrel-extension and bolt held!
When using standard AR-15 barrel-extensions, a thread-relief groove must be used so that the barrel-extension can be screwed down tight to the shoulder. This is the way the prototype WSSM extension was made. When the destructive test results were being examined, it was found that there was a very slight bulge in the chamber where the thread-relief groove was. The WSSM barrel extension was modified slightly so that no thread-relief groove is necessary. The was the ONLY change that was made.
The reason I have been refering to the "WSSM" bolt and barrel-extension all this time is because the bolt/carrier and barrel extensions for the WSSM is what I am using for the BR uppers. The bolt-faces just are not opened up as far as what is necessary for the WSSM case-head.
There's quite a discussion about the 6BR in an AR space gun upper over at The Highpower Journal.
http://forums.delphiforums.com/flahighpower/start
You need to register with the moderator to post comments or replies but I think you can read it without having to be a registered member.
The thread is entitled "6mm Spacegun" thread #13170. Comments about a 6BR start about post # 3 & run thru #45 or so.
From post #37:
"The first question was about the "meat" in the barrel threads. The dimension of the hole in an AR-15 that accepts the barrel extension is 1.0" which means that you have to turn down the barrel to .812 in order to thread the end of the barrel for the extension. Once you get through cutting the threads, you end up with a major diameter,.812") and a minor diameter of approximately .725". If the 6mm BR has a body diameter of approximately .5", you are only left with about .110-.120" of wall thickness in the thinnest part of the chamber. A chain is only as strong as the weakest link. In my opinion and in the opinion of many accomplished and well known gunsmiths, that is too small a margin to work with in regard to safety, especially when half the guys out there are pushing the pressure to the limit in hopes of improving their scores."
http://forums.delphiforums.com/flahighpower/start
You need to register with the moderator to post comments or replies but I think you can read it without having to be a registered member.
The thread is entitled "6mm Spacegun" thread #13170. Comments about a 6BR start about post # 3 & run thru #45 or so.
From post #37:
"The first question was about the "meat" in the barrel threads. The dimension of the hole in an AR-15 that accepts the barrel extension is 1.0" which means that you have to turn down the barrel to .812 in order to thread the end of the barrel for the extension. Once you get through cutting the threads, you end up with a major diameter,.812") and a minor diameter of approximately .725". If the 6mm BR has a body diameter of approximately .5", you are only left with about .110-.120" of wall thickness in the thinnest part of the chamber. A chain is only as strong as the weakest link. In my opinion and in the opinion of many accomplished and well known gunsmiths, that is too small a margin to work with in regard to safety, especially when half the guys out there are pushing the pressure to the limit in hopes of improving their scores."
The diameter of the WSSM barrel-extensions is not the same as the AR-15 barrel-extensions. Everything about the WSSM is larger than that of the AR-15. I would think it would be crazy to try and open up an AR-15 bolt far enough for a BR case-head, not to mention the lack of "meat" over the threaded shank.
I would have to agree. If you were to put the body of a wssm inside the threaded shank for an AR-15 barrel-extension, it would be too thin for my tastes. Keep in mind what I said in an earlier post: We blew the bottom right out of the bolt-carrier and all it did was make a slight bulge in the chamber where the, now nonexistent, thread relief groove was. And this was on a WSSM case. The smaller BR case wouldn't even be close to bulging the chamber-wall.
I would have to agree. If you were to put the body of a wssm inside the threaded shank for an AR-15 barrel-extension, it would be too thin for my tastes. Keep in mind what I said in an earlier post: We blew the bottom right out of the bolt-carrier and all it did was make a slight bulge in the chamber where the, now nonexistent, thread relief groove was. And this was on a WSSM case. The smaller BR case wouldn't even be close to bulging the chamber-wall.
I was going to have it to you by Christmas, but I've gotten a bunch of people that wanted to shoot it first, so I'm going to be passing it around a little.
It won't be as long as I though though, one of the guys that was going to try it out, decided not to when he found out Wolf didn't make ammo for it!
I shouldn't do that to you this close to Christmas. I'll keep you posted.
It won't be as long as I though though, one of the guys that was going to try it out, decided not to when he found out Wolf didn't make ammo for it!
I shouldn't do that to you this close to Christmas. I'll keep you posted.
Don't let them burn up the barrel.:nono:That photo back on P3 shows 2 AR15 bolts, 1 Oly wssm sized bolt for a 6BR and a 308 AR10 bolt so you can see the difference in the size of the bolts.
You would figure from there that the extension and barrel must be larger to handle that 3rd bolt.
You would figure from there that the extension and barrel must be larger to handle that 3rd bolt.
The Magazine insert that goes in mag works well in my Hagar.
I'm loving the gun so far and feel that once i've finished fireforming 500 cases it's still holding under inch at 200.
The cases that have been resized and trimmed for lenght are inside/outside neck turned to chamber deminitions and surely need it for some will hardly be touched and some take off alot.
Molly coating the 88gr.and seating to mag length is still up in the air but H322 looks promising.Berger 105's with VV150 also show promising results in single shot.
I would like to try the VV140 powers but cannot locate it.
Love the AR feel it might be even better in gas-piston model with the 4oz.trigger.
I'm loving the gun so far and feel that once i've finished fireforming 500 cases it's still holding under inch at 200.
The cases that have been resized and trimmed for lenght are inside/outside neck turned to chamber deminitions and surely need it for some will hardly be touched and some take off alot.
Molly coating the 88gr.and seating to mag length is still up in the air but H322 looks promising.Berger 105's with VV150 also show promising results in single shot.
I would like to try the VV140 powers but cannot locate it.
Love the AR feel it might be even better in gas-piston model with the 4oz.trigger.
The Magazine insert that goes in mag works well in my Hagar.
I'm loving the gun so far and feel that once i've finished fireforming 500 cases it's still holding under inch at 200.
The cases that have been resized and trimmed for lenght are inside/outside neck turned to chamber deminitions and surely need it for some will hardly be touched and some take off alot.
Molly coating the 88gr.and seating to mag length is still up in the air but H322 looks promising.Berger 105's with VV150 also show promising results in single shot.
I would like to try the VV140 powers but cannot locate it.
Love the AR feel it might be even better in gas-piston model with the 4oz.trigger
I hope my 6BR shoots that well. What brass do you use for the Hagar? I hope the Lapua brass I will be using doesn't need any turning with the no-turn neck that Mike,dtech) is chambering for me. This 6BR stuff is new for Mike,and Me) so he is being real careful with it. I hope to use 105 Bergers for the 600 yd prone and something lighter for prairie dogs. I have some alreaded loaded with 29 grs. of Varget to try when I get the upper. I will adjust the OAL when I get it.
Jimmy
I'm loving the gun so far and feel that once i've finished fireforming 500 cases it's still holding under inch at 200.
The cases that have been resized and trimmed for lenght are inside/outside neck turned to chamber deminitions and surely need it for some will hardly be touched and some take off alot.
Molly coating the 88gr.and seating to mag length is still up in the air but H322 looks promising.Berger 105's with VV150 also show promising results in single shot.
I would like to try the VV140 powers but cannot locate it.
Love the AR feel it might be even better in gas-piston model with the 4oz.trigger
I hope my 6BR shoots that well. What brass do you use for the Hagar? I hope the Lapua brass I will be using doesn't need any turning with the no-turn neck that Mike,dtech) is chambering for me. This 6BR stuff is new for Mike,and Me) so he is being real careful with it. I hope to use 105 Bergers for the 600 yd prone and something lighter for prairie dogs. I have some alreaded loaded with 29 grs. of Varget to try when I get the upper. I will adjust the OAL when I get it.
Jimmy
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