The barrel and receiver have to be machined to accommodate a 3 1/2. You can engineer and machine a barrel and receiver to 3 1/2" standards and shoot 3 and 2 3/4 but not practical or cost effective to go the other way. Many factors included, receiver length, receiver ejection port opening, recoil spring strength, slide length and chamber and barrel machining are only a few things required. IMO, if you think you may like to shoot 3 1/2's, either turkey or duck and goose loads, then buy a 3 1/2, you can go down in shell length, if you like. Once a gun is engineered and machined for shorter length shells too many factors to go up.