Bob,
My BSS boxlock had 3" chambers, while my sidelocks have 2 3/4" ones. The barrels on the sidelocks are trim and light giving them a lively feel. My 12 and 20 handle similarly with the nod going to the 20 for being lighter and trimmer. I feel that with the 26" barrels both guns have a more neutral balance, something I now appreciate having had shoulder surgury. I have learned through muscle memory to shoot the lighter guns effectively. If a little more weight forward would be desired, the one's with 28' tubes should be considered, although they are not encountered as often.
DJG had an article a couple of years back about "Brownings Best" showing the two different engraving patterns. The article was by Colin McLagan in the Autumn 2003 issue. Nick Hahn wrote a nice article in the Summer 2009 issue of DGJ on the BSS boxlock and it's different grades.
Karl
