Looking into the 243 BR-K

[coyotehunter]

I'm looking into building another rifle. It will be some form of 6mm. Seriously considering the 243 br-k and was wondering if any one as tried it. I like the fact that I can uses my 6br seating and neck sizing die that I already have. Also if you have to full length size what do i need to use? Gonna use a Broughton 5c barrel in a 1in7.5 twist or a 1in7 want to try some 115's also is this twist to fast for the 107 sierra?

 

[joemax]

Great cartridge. Easy to form. I had a 243 winny full length sizer ground down and decapper removed to push the shoulder back for fireforming. After fireforming, for resizing I use a forster bushing bump die in 6br with a .243 decaping rod. This die only resizes the neck and bumps the shoulder back .001-.002" for easy chambering. You may not ever need to FL size the brass. Stable brass is one of the intended characteristics behind the design when loaded to reasonable pressures. Hot loads are going to stretch any brass to some degree. Otherwise, I think a custom FL sizer or body die is the only solution.

I don't know if the core will seperate and spin or not. I would guess not. A call to Sierra would answer your question.


Joe

 

[rcw3]

I am not sure why you would go with the 243 BR-K when you can use the 6mm Super LR and obtain factory dies which are available for the 6mm Super LR (but not the 243 BR-K). The two cartridges are almost identical.

http://www.6mmar.com/Super_LR.html


For barrel twist, never (and I mean NEVER) go with a 1:7" twist 6mm. We did a lot of testing and the 7" twist 6mm barrels are problematic - the twist is so fast, most 7" twist barrels show a lot of pressure even at moderate loads. With a 7.5" twist that has not been an issue, but with a 7" twist you are either right "on the edge" of being too fast for a twist, or "over the top" and you will get a lot of pressure every time you try to get the velocity going above a mild load.

Robert

 

[cmillard]

Robert, you bring up a good point on twist. not to change from the original subject, but the same goes for people thinking they have to get a 6.5 twist to shoot 90 grain bullets in .224. i have successfully shot 90 bergers out of my 18" 1-7" long range ar-15. and that was at moderate velocities and at 400 yards