Bayard SxS chambers

[longshot7.62x51]

I have a 12 gage Bayard shotgun I am trying to resurrect it has fluid compressed steel barrels. No nitro proof marks. I am trying to determine if the chamber is for 2 1/2 in shells or 2 3/4 inch shells. I know it will be black powder. Can I use Brass shells. And does any one have a light load I can use once it is finished. Photos to come

 

[Bull Nutria]

I suggest posting your question on shotgun world forum in the gunsmithing sub forum.

Bull

 

[Jim Watson]

A European shotgun not marked otherwise will have 65mm = 2.55" chambers.
If 2 3/4" it would be proof marked 70mm.