Heavy clothing produces similar results to animal hide, I've read numerous times on this forum. So here, let's see what a 150gr bonded .308 load does...
http://www.le.vistaoutdoor.com/ammun....aspx?id=24457
Looks like 18" of penetration and 0.75" expansion.
http://www.le.vistaoutdoor.com/ammun....aspx?id=24475
75gr .223 looks like it manages 16.75" of penetration, and 0.57" expansion.
Obviously the .308 will be a bit more destructive, but we can also see above that the .223 expands and has enough KE to provide damage...but let me ask you about those angles again...what angle, exactly, are you counting on that extra 1.25" giving you that the .223 shooter will be denied?