I can't speak for the other makers, but LC 12 gauge chambers were bored 2 3/4" standard; if they were other than 2 3/4", there would be an oval stamp on the barrel flats stating "Chambers 2 5/8 Inches" or "Chambers 3 Inches", etc. As I recall, prior to chamber length standardization on late vintage LC's, twenty gauge chambers were bored standard at 2 1/2" and sixteen's at 2 9/16". I've seen some early small bore LC's with odd chamber stamps; an A-3 twenty with chambers marked 2 3/4" and a 16 gauge Specialty (I believe) stamped "Chambers 3 Inches". It's still a good rule of thumb to always measure chamber length on any vintage gun to be certain.
