Are you saying that the -1 cylinder is longer than a -2? Naturally it will be longer by the width of the rim, but that doesn't affect the length of the chamber. Educate me please.
My 4" Model 66-1 has cylinder counter bore, but no pinned barrel - SN 113KXXX, placing it as 1981 manufacture. (This was one of 1,500 that were Va./SP 50-year commemoratives, delivered in April 1982.)