Originally Posted by jimbob86
Anybody got an idea what that might be? 6mmBR?
Well, it's an odd way of referring to it, as a "243 short" as it's not the same relationship as a 22 long and short, for instance, but there is both the 243 Winchester Short Mag and Winchester Super Short Mag.
The later of which is an incredible but unfortunately "factory dead" cartridge. It will push a 55gr bullet almost 4,200 fps.
I'm looking for one now if anybody has one to get rid of... I've got a 270wsm for trade.