An 8-bore action is coming up for auction at the next Holt's auction and I wondered what were the possible calibre choices of double rifle to fit this action - assuming that the action was suitable etc...?

This lead me to thinking what are the suitable calibre conversions for the other shotgun sizes with a view to creating a well balanced, safe and elegant double rifle?

8-bore

10-bore

12-bore (3")

12-bore (2-3/4")

16-bore

20-bore

28-bore

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