^^^I do remember those Nightguards when they came out. Proof that S&W can do it if they feel so moved. Heavier than a 2" model 12 from back in the day, but a cool idea with the sights. I'd think a modern, DAO scan ti M12 could be brought down to 16-17 oz. Depends how much weight could be saved in the cylinder, I suppose.
on edit: a quick trip down wiki lane shows that the first 12s--the ones with the failing cylinders-- came in under 15oz. A robust K-snub coming in at 16-17 seems totally doable. Of course, so does a rocket car.