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Rechamber 6BR To 6BRA

james

Gold $$ Contributor
I’m thinking of re-chambering my BAT straight 6BR Brux 1x9 twist 26” barrel to 6BRA. It shoots well however just wanting to try something different. I have 2 other 1x8 twist barrels I can use with the BAT. This barrel only has around 250 rounds on it. How much barrel length would I lose in the rechambering process?

Worthwhile project? Primary usage would be a few varmint matches during the year. Again would like to tinker with something new.

Thanks!
 
The BRA head spaces a few thousandths shorter than the BR so tenon and shoulder would move up/forward a bit. What more comes to mind is what your current neck dia, throat and freebore dimensions are and how they may or may not match and ultimately clean up with the new chamber.

Do you know what reamer was used for your chamber? Do you have a reamer print for it?
 
Personally, if you have a fresh barrel I would go that route. When looking for absolute accuracy many things can and do go wrong with re-chambered barrels. Many times it is not as simple as just setting it back one thread and off you go. Been there and done that, and it was not good. Good luck and keep us updated.
Paul
 
Personally, if you have a fresh barrel I would go that route. When looking for absolute accuracy many things can and do go wrong with re-chambered barrels. Many times it is not as simple as just setting it back one thread and off you go. Been there and done that, and it was not good. Good luck and keep us updated.
Paul
Sounds like I had better rethink rechambering my existing barrel and look at a new barrel.

Thanks
This is the best advice you will get. Depending on round count and barrel overall condition (fire cracking, rough throat, etc) just going in with a BRA reamer could be disaster. Also, as mentioned above, dependent on the headspace of the existing chamber, you could run into an issue with the headspace differences between BR and BRA. Usually this can be overcome through various methods but it's possibly another headache you don't want.
 
Also, as mentioned above, dependent on the headspace of the existing chamber, you could run into an issue with the headspace differences between BR and BRA.
The difference in headspace is -.004" for the BRA to BR so only minor and easily attained changes to tenon dimensions would be needed on that front. The other dimensions mentioned would be far more important to the question.
 
Sounds like I had better rethink rechambering my existing barrel and look at a new barrel.

Thanks
That's where I'd go especially if you don't know what reamer was used for the existing chamber. Leave the BR barrel that "shoots well" alone and chamber up one of your other barrels to the BRA.
 
The difference in headspace is -.004" for the BRA to BR so only minor and easily attained changes to tenon dimensions would be needed on that front. The other dimensions mentioned would be far more important to the question.
I was thinking that the BRA uses a .014" crush on the BR go-gauge.
I have one BRA barrel that BR brass will close easily on and fired datum measurements are a least bit longer than all my other BRA chambers. It works just fine and have had zero issue with misfires.
My personal experience says the most troubling issue could be excessive pressure when rechambering without cutting off the tenon on higher round count barrels. I once did this with a Dasher barrel to 6 Creedmoor. Immediate pressure issues with ammo well under max charge weights. A close inspection revealed the new chamber did not remove all the fire cracking. For experimental purposes we cut off the tenon and ran that same reamer back in. The problem immediately went away.
 
Not aroute that I would choose, and there is a better option. I had a well used - but still shooting BR into BRX done - 'cos I had the use of a reamer and it's an easier rechamber. Another advantage is to using your existing dies just move them up 100 thou. The BRX has roughly the same capacity as the Dasher.

If it's speed that you are looking for , an alternative (don't shoot me, purists!) is to increase the load of the BR - with H4895. I had seen good results with in Lapua BR brass, and exceptional accuracy with 107g SMK. CCI450's needed. I have yet to try a load with 95g SMK's. Please use common sense when playing with loads like this - I am using a Barnard action - no ejector and a small firing pin etc.

Seems that I'm going the Dasher route, as I have just had an Alpha Dasher built and just aquired a 6mm Proof profiled blank- 8 tw and some Norma Dasher brass - which won't work in the Alpha chamber. That one can wait until I have an action etc available.
 
I was thinking that the BRA uses a .014" crush on the BR go-gauge.
I have one BRA barrel that BR brass will close easily on and fired datum measurements are a least bit longer than all my other BRA chambers. It works just fine and have had zero issue with misfires.
The regular 6BR go gauge is a no-go for a 6BRAI, so if it closes on a 6BR go, then it really isn't a 6BRAI.
 
https://ackleyimproved.com/chambering-for-ackley-cartridges/
For the uninitiated out there…

Rimless improved chambers, when properly headspaced, allow the shooter to fire the factory parent cartridge in the new improved (oversized) chamber safely. This is because the cartridge is headspaced on the junction of the neck and shoulder. Traditional Ackley gauges utilize a go gauge that is .004″ shorter than the factory or SAAMI go gauge. Because only a small point on the shoulder is in contact with the chamber it is easy to crush the shoulder as the bolt closes. When fired the brass stretches to fill the new improved chamber. This is what is known as fire-forming. Want to learn more details of Ackley Headspace and Chambering? Click Here.
 

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