No experience with 6BR, but have interest in that cartridge, and others like the 6 Dasher, 6x47 Lapua, etc. All for the same intended uses at my 6.5 CM (in the works), but still definitely interested in folks with experience in those 6 mm cartridges.
The small rifle primer use is another aspect that had me going with 6.5 CM. If the component market was better, I probably would have given other cartridges more consideration. A friend of mine is interested in the 6/6.5 PRC. All seem to have their fans. I usually am one who wants to try for myself, but likely not in this case, or at least for a while down the road.
Just did a quick search of 6 BR brass (6 BR Norma?) and found a lot of vendors have it in stock. Darn. Maybe I should have gone with that instead of 6.5 CM. I'm kidding, mostly. . .
Do you at least have finalists for your new rifle? Or still in the brain storming phase?
Anyways, good luck! It's addicting. . . more than the black rifle disease. . .