Need a barrel for my Winchester Model 1200 Police Stainless Steel 12 guage. Looking around for it, the best I could find was a Model 1300 Marine 18 inch barrel. I'm looking to get something SS and 18". The thing is they all say either 5 or 8 shot magazine tube. My tube will hold 6 rounds in the tube, one in the chamber for a total of 7. Will either of these barrels work?