Also a Chinese company produces some strange turrets (brass barrels included) some of which have 18 and 20 inch guns. They show up about every month on Ebay. Some are active right now if you search for "1/700 resin turrets". One is listed as "1/350 1/700 USS Montana/Ohio 457mm MKA Turrets+Metal Gun Barrels Detail-up Part"
Next month I will be 71 and it is possible that in my aging mind I believe I saw 18" and 20" turned brass barrels for Iowa and Montana class ships in 1/700. Somebody tell me its true and guide my old carcass to a site I can rejoice in. I intend to push the limits of the possible with a few of my BBs. I apologize for not coming the the good old site often enough. I will repent straightaway. Thanks gents.