Re: group size
I use a 6mmBR for varmint shooting. Shooting 87grain V-max at 3000fps out of a 27inch 1-10 Twist I get about 1 inch 5-shot groups. I would consider 1.5 inches to be good. I haven't shot my BR beyond 400yds (not yet anyway) due to the land I shoot on. For rabbits, magpies, wild cats (the domestic version) out to 400yds its OK. Have also used it on wild goats out to 200 yds.
Glen - New Zealand