I addressed tis very question to a German manufacturer of insert barrels in calibers up to and including 9.3X74R. I specifically asked how they would rate the strength of the Krieghoff "Teck" over and under combination gun.

This is the answer I received:

Sehr geehrter Herr Warren,

wenn die Kippwaffe ein Stahlsystem hat, kann man fast alle Kaliber einbauen
(bei starkem Verschluß muss evtl. der Schlagbolzen verkleinert werden).

Für Fragen stehen wir auch gerne telefonisch unter 0049 791 74/82 zur
Verfügung.

Mit freundlichen Grüßen

Keller + Simann GmbH

i.A. Susanne Karcher

Dear Mr. Warren,

if the break action is made of steel, almost all calibers can be built into it (possibly the firing pins [and holes?] would have to be reduced in size).

We will be happy to answer your questions over the telephone at 0049 791 74/82.

With friendly greetings,

Keller + Simann Inc.

Susanne Karcher