got to checking my 12ga & 20ga 1200’s & came to the idea that the breech bolt & feed throat & of course the Barrel are the only thing that’s different on each gun??? the Receiver is the same on all models!. If that’s the case then changing those 3 pc’s does that make it that easy to change one from a 12ga to 20ga to16ga??..of course the serial # wouldn’t match!??? please let me know what you’ll think?? trigger assy are the same also!