Energy is a great number for the side of ammo boxes and it allows me to compare how a cartridge relative to others will whack ya on both ends, but it's not really the whole story. I think the 6.8 SPC came from someone getting real about combat. First, solders need something for 0 - 300 yards. With most shots being 0 - 50 yards. Now compare the balistics in these ranges. Not so bad, eh? Now why the 6.8. . . .because killing is related to energy expended. 223 tends to explode when it hits bone or just put little holes in you. The 6.5mm bullets and larger, especially when driven slower will expand and not blow up. This makes for a bigger hole in and out. Now with FMJ, not sure how well they can make that work, but it still makes a bigger hole than a 223.

A 30-223Rem might also be great, but then, what do I know![:@] Dang it, the Russians already made the 7.62 x 39. Can't copy that.