I see a Model 12, 121, and 1200 but no model 120, so first verify the model number.
For a barrel, try gunpartscorp.com, auctionarm.com, and gunbroker.com then start hitting the ads in Shotgun News. The model 120 was really a model 1300 slow budget model. It is the same inside the only difference is the wood on the 120 is plain hardwood. Where as the 1300's were offered with pressed checkering and also in synthetic versions. Here is a link to barrels that are made for the 1300's that will fit the model 120. http://www.midwestgunworks.com/merchant2/merchant.mvc?Screen=CTGY&Category_Code=winchester-model-1300-barrels
At this time no,there are not any available.You could have a model 1300 slug barrel redone and have the gas ports added to this barrel.Then it will work fine in your model 1400 Winchester shotgun.
Yes, I don't think you should have a problem, but your pattern may not be consistent.
Try e-gunparts.com, MidWest Gun Works, Shotgun News, gun show, gun shop.
I have one that I would sell.
"Your" Winchester Model 21 Double Barrel Shotgun was manufactured in 1933, giving it an age of 77 years, as of 2010.
Your Winchester model 1911SL(self Loading)shotgun was first made in the year 1911.
Not anymore but I hear you can take a 1300 barrel and have gas ports added and that should work.
The model will be stamped on the barrel right after the Winchester name.
Please include the model number of your Winchester shotgun to get a correct answer to your question along with the serial number.
The Winchester Model 21 Grand American 3-barrel cased set. Bert H.
You will need to include the shotgun model number,or model name.Type of shotgun(single shot,pump action,double barrel,or semi-auto)along with the serial number that you have provided to get the correct age of your Winchester shotgun.
Look on bottom of receiver and barrel