The 6br is a great cartridge & yes it's only 100-200fps behind the 243win. However, no matter what cartridge; the longer barrel will give you more velocity (ie a 28" 6br loaded hot will be faster than an 18" hot 243). A general rule of thumb is expect 25fps velocity gain every inch of barrel.
I've not shot a ton of light bullets (under 70gr) in my 6BR's but the velocities quoted from the site look a bit optomisic. I'm not running anything close to what he is claiming with my 20" 6BR with the 85-95gr class bullets. You can probobly get there but your going to trash the brass running it that hot. I usually get better accuracy away from scorching hot anyway. That's what I look for most & where the 6BR rules.
