It appears to have been re-proofed. The barrel marked .405 and now 10.2mm is now .4015 (+?) and the .400 now measures .425 (+?).

Are you sure you have got them the right way round?

Photos would help.

They indicate the bore diameters at 9 inches from the breech face and are nothing to do with the chokes.

Last edited by Parabola; 02/14/23 05:01 PM.