The sidelock BSS shares little more than the name of the boxlock guns. I have 1 12g BSS (my first sxs) and 3 20g BSS guns, all boxlocks. All of them have very thick (.045-.050) barrel walls, making them heavy for their gauge. That's a trait they carried over from the Citori line. I shoot them all pretty well. The 20 ga guns are all between 6 1/4 lbs and 6 3/4 lbs.