Chasseur:

Many thanks for the informative reply.

Geoffrey Boothroyd, who knew more about shotguns, especially British ones, than everyone else (not anyone, everyone) wrote extensively about both the sidelock and the boxlock action. However, and this is not well known but it is established, he shot a Dickson round action. I think that may well settle the whole argument.

Gerald,

Its a hard question to answer. The guys who love side locks will tell you flat side locks are better in all ways. I think in a general sense there is something to this. Sidelocks are considered "fine" guns so more time and effort goes into making them in general, so there is a greater chance the triggers are light and crisp, etc. However there are nice well made boxlocks out there. For example, I'd be willing to beat that more work and care went into a old Westley Richards boxlock, than your adverage modern Spanish side lock. Not that the Ayas, Grullas etc are not nice guns, but there are nice boxlocks out there.

Hope this helps.