From the beginning, unless requested otherwise (and so stamped) 12 gauge hammer and hammerless L.C. Smith chambers were 2 3/4".
A 1898 Crown Steel Pigeon Gun
2 7/8" & 3" chambers were not uncommon on guns for Live Bird and Inanimate Target shooting - not for more powder or shot but additional wadding.
Unfortunately the 1890 - 1913 Hunter Arms shipping records, unless for a high grade gun, have limited information and are unlikely to document a special order chamber length.
It is not uncommon to find barrels with lengthened forcing cones that have had the chambers lengthened in the process
Threaded Mode