1954 Rules of Proof List only 2 lengths for 10ga 2&5/8th , 2&7/8th inches which were pretty much std from @ 1900 onwards other variations were made special order and the Proof house would test based on info supplied by the maker . I seem to recall 3 &1/4" was not unheard of for wildfowling guns.


Hugh Lomas,
H.G.Lomas Gunmakers Inc.
920 876 3745