I have one chambered for 9.3X74R but have not handled one in a smaller chambering. My guess is the barrels down to 8mm would be the same dia as the 9.3, but the ones smaller would be lumped into a smaller dia barrel. You could be right however, they may all be the same dia from 9.3 down. In any event, even the smallest chambering would not be overly heavy for caliber. My 9.3 handles like a nice 410 shotgun, and feels lighter than it is. It weighs in at 8.6 lbs! That seems very light to me, because most of my doubles weigh 10.5 lbs up!