Vol,
A light, less than 7# RBL 12 will be very hard to find. There is one out there that was 6#9 0z, it was gone before I could get out my CC! That gun was on a 16 Ga frame as btdtst's gun. I have a 16 ga that is not heavy at all, 6# 3 oz. It is rare among its peers. Most push 7#. I've hunted with it almost exclusively for three seasons, I am very satisfied with the gun, in all aspects.

You may have more success trying to find a Ruger gold label. Occasionally one shows up for sale. They are supposed to weigh in around 6.5#. I have my doubts as the few I see advertised are closer to 7#. Those that have them seem to like them.

Chief