xausa,
Thanks for making my point! Even though your gun is made on a 16 gauge SIZE frame, it was always made as a rifle and there are probably some subtle differences, such as firing pin diameters, huge bolsters at the bend, etc. In any case, the Kersten lockup is one of the strongest lockups ever known or produced because it has two crossbolts, one on either side of the barrels and about as far away from the hinge as possible. If your gun had been made originally as a 16 gauge Marlin over/under shotgun, would you want to shoot it as a .458 conversion gun? I didn't think so.
Simply stating that your .458 is the same action size as a 16 gauge over/under, does not tell the whole story by a huge margin. I am trying to help these beginners think of conversion rifles in a safer and more conservative light. Yes, many calibers can be used in double rifles, either side by sides or over/unders, but many are not suitable for beginners to be making up on shotgun frames, especially when they are of dubious strength.
Showing them your .458 on a 16 gauge SIZE frame is not helping me to constrain their enthusiasm for large bore, handmade conversions.
I personally love your Krieghoff rifle, it has one of the very best actions out there. I am currently thinking along the lines of converting my Ithaca 12 gauge model 500 into a .450 #2 Nitro Express rifle. It also has the double bites of the Kersten lock up system. Because of the larger case, the #2 has less pressure for the same loads and I have no doubt that the Ithaca will handle the strain. Thanks for sharing your wonderful gun with us. Bob