I believe Blackhole weaponry runs the 6mm version on Grendel brass called the .243 LBC. I'm running a similar 6mm version on a Grendel case called a Fat Rat which blows the case shoulder forward with a 40 degree angle. Not quite sure of the advantages yet, but it does give me enough room for 30 grains of Varget and a 70 grain Nosler boat tail for coyotes. I also have a 6x47 Lapua bolt gun and I run 36.5 grains of Varget with the same bullet......it's a coyote hammer. Just to give you an idea of the different case capacity. I'm looking for some great things with the Grendel case because it puts me very close to what I use in a standard 6BR case in a standard AR platform.
Kevin