"the 19 is a K frame. The 686 is the larger L frame and the 27 is the even larger N frame.

"Each gun is bigger than the other in about all directions and for sure by weight."

Actually, the .357 L frame is heavier than the .357 N frame when barrels are the same. Catalogs list the 6 inch M-686 as 46 ounces, and the 6 inch M-27 as 44 ounces. The original L frame barrel's underlug is quite heavy.

I believe that, until the X frames, the 8-3/8 inch L frames were the heaviest production handguns S&W had ever made.