For what it's worth, my Krieghoff .458 Winchester Magnum is built on a 16 gauge frame, simply because Krieghoff did not build anything larger than a 16 gauge on its "Teck" O/U action in 1970. The same action was also fitted with a pair of .375 H&H barrels. I killed four of the big five with that rifle in Africa, and never had a problem with it.

To be sure, the action is a double under lug, Kersten Verschluss action, which is extremely strong by any standard.