Jent had a 1945 Marlin gun 16 ga barrel hanging in his basement. Just for grins, we tried it on my 16 and it fit perfectly! Unfortunately the top rib was not present. So if anyone got a (1945 plus) 16 ga top rib or wrecked barrels with a rib, leave a reply at your leisure. I 'd like to "Make a deal".
Good Shooting to you.