FWIW, The last significant power change to shotshell ammo, other than elongation ( to 3" or 3-1/2" shells ) was in 1926.
AFAIK, Both of your shotguns should have 2-3/4" (70mm) chambers.
"16.5" & "17.1" are bore measurements, indicating the amount of constriction, i.e., choke.
Your Beretta 412 was known as the Folding Companion - the loads shot through it should take it's light weight into consideration.
Your Verney Carron Luigi Franchi Automatic is a clone of the Franchi AL-48, a long-recoil autoloader -
and while it's safe with all 2-3/4" loads, the bevel on the friction ring around the mag tube, just ahead of the recoil spring (under the forend wood) MUST face in opposite directions for heavy (magnum) or light loads -
shooting heavy loads with the bevel in the "light load" position will damage the forend and maybe the receiver; shooting light loads with the bevel in the "heavy loads" position may cause misfeeds.
Last edited by PetahW; March 2, 2013 at 08:26 PM.