Looking for a doublebarrel rifle, I couldnt find anything bigger than 375H&H oer 375 flangged in an U/O rifle. Is that a limit for such a construction. Do you know bigger ones?

Burkhard

CZ made a .458 Win Mag. I think I have heard of a .470 Nitro, but I would have to look it up. Many prefer the side-by-side for dangerous game, so that may explain why more of the larger calibers are in SXS configuration.

Edited: I did a quick look-around and see other references to .470 O/U. I doubt there are a lot of them, but it seems they were made.

I have seen several 458 Winchesters and two that were reamed to 458 Lott; Robgunbuilder's CZ and a custom guild gun. Both had the 300 series U/O action with kirsten cross bolt. That's a damn strong action and should take anything you can fit in a S x S with a breech the size of a 12 ga.

Heym builds their model 55 o/u in 470.

The 55 series is on the action I'm describing. I spelled Kersten wrong, as usual.