Another S&W head scratcher... My 4013's label says 3-1/2" bbl. & my 4516-1's says 3-3/4" bbl. If you measure them from the bbl. tip to the breach end of the chamber, not the hood extension but just below it, both of them measures within 0.05" of 3-1/2". Of course the bbls. aren't really even that long either. If you measure from the chamber's shoulder, where the case mouth headspaces on, to the tip of the bbl., they're realistically 2-3/4" barrels.