This will not fit a model 12
No.
Yes the stock on a Winchester Model 12 16 gauge is the same as a 20 gauge. 16 gauge,20 gauge, and 28 gauge are all the same for the Winchester Model 12. Thanks, Tim
No
take it to a gunsmith
Your winchester model 12 shotgun was made by winchester in 1950.
Your winchester model 12 shotgun was made by winchester in 1956.
Your winchester model 12 shotgun was made by winchester in 1928.
The most telling feature is the way that each fits there respective receiver tangs.The model 1897,and the Model 12 were different designs,thus the tang on each has different dimensions.
Your winchester model 12 shotgun was made by winchester in 1939.
Your model 12 Winchester shotgun was made by Winchester in 1926.
No