While I did not say so in my first post obviously the firing pin centers would also be different for each gauge. This difference becomes obvious on the .410 as the breech is little wider than the action body behind it. Probably the hammers are the same but the firing pins would set at different angles. Not having any in front of me but just going on recollections of those seen this would seem to be the case.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra