I have a remington 870 wingmaster 12 gauge. Its about 20 years old. It says on the side of the barrel 2 3/4in. Does anyone know if it can handle 3 in. or 3 1/2 in. turkey loads?
No.
It's for 2 3/4" only. The side of the reciever will indicate the chamber capability.
Note: 3" chamber barrels will fit on 2 3/4" recievers And will fire 3" shells, but are not sopposed to/not recommended. 3 & 3.5" guns are dirt cheap in express 870's. If you really need one, pick up another gun.