BR Cartridge

[blackfoot]

I was of the understanding that the BR family of cartridges would not work in an AR upper? How does this guy do it? I imagine there are some issues to overcome and they don't mention anything.

http://www.ar15performance.com/6_5br_

[LRRPF52]

He makes a larger bolt and a larger barrel extension to take an AR10 size bolt face, lug mass, etc., while still fitting in a standard AR15 carrier and upper receiver, with no mods to the upper. Anything larger like the Olympic Arms WSSM chambering require an upper with a larger inner diameter for the barrel extension.

I think the BR bolt, but with a .444"-.450" bolt face would make a great bolt for the Grendel, since the Grendel case is actually a high-pressure component, limited currently by the modified 5.56 bolt with minimal material in the lug roots and bolt face web. You would be able to push the cartridge with velocities maybe 100fps faster with the BR bolt using a correct bolt face for the Grendel.

[stokesrj]

Also for those who may not be familiar with Criterion barrels, it is a subsidiary of Krieger that are button rifled not cut like the Krieger. My experience with them has been that they are a good barrel similar to a Douglass and with wear characteristics like one also. Expect about half the life of a cut rifle barrel but similar accuracy.
Bob

[sititunga]

Harrison`s 6mm BRX project was the most interesting. BRA Technologies (http://www.bratrifles.com/) also offer the BRX, but they use an Oly bolt/carrier and barrel extension designed for the WSSM line of cartridges. I`m surprised more AR15 makers haven`t developed this further. The BRX gets you pretty close to 243 velocities.

[elkbow]

yea Harrison and ARP definitely knows about AR platforms. The 6.5BR and BRX aren't for the faint of heart though, you have to know what you're doing when loading as you will need to make or form the brass, use the proper neck sizer, and develop some loads for it. The Kreiger Criterion is a button rifled barrel, but the idea of this barrel from ARP isn't for winning 1000 yard matches but to be faster than the grendel for the same length barrels and to be used for hunting to reasonable distances.