Joe: Sorry to be the bearer of bad news, but I think most here will agree that it's not a good idea to shoot steel through any Model 12 you care about. As I understand it, damage is possible in two ways. First, the steel in the shot is harder than the steel in the barrel, so the shot column will score the bore as it travels to the muzzle. Second, the tighter the choke (Full in an original Duck gun), the more likely the steel shot will jam up at the choke and cause a muzzle bulge or worse. Steel shot has no "give" to it, whereas the lead the Model 12 was designed for is softer than the barrel steel and will "rearrange" itself as it passes the choke. Shooting steel, at best, you'll much more quickly wear our a classic, high-quality, carefully choked Winchester barrel ... and the scenarios get uglier from there.
That leaves you with three choices: 1) Find another gun to shoot waterfowl with. 2) Open up the choke to IC or Mod, which would avoid the chance of bulging and probably work even better ballistically. 3) Shoot a non-toxic lead substitute like bismuth, which kills like lead and works in a Full choke. The problem with #1 is you want to shoot ducks with your Winchester, and I don't blame you. The problem with #2 is that it costs money and ruins the gun for guys who prefer original guns and option #3. The problem with #3 is that the new shells cost a small fortune. One other option occurs to me ... you could save the original barrel for special occasions and the trap range, and find a spare barrel that some other guy already paid to open up. Good luck, whatever you do. TT
