I'd like to start bird hunting(waterfowl and turkey) and was wondering if a 20 gauge shotgun would be sufficent. I know when bird hunting you are constintly shooting and the 12 gauge will become a pain to shoot. I was also thinking of getting a shotgun with changable barrels. This way I can hunt turkey, waterfowl and throw a rifled barrel for slugs to have a deer gun aswell. So my question is which would be a better gun for what i'd like to use it for. 12 or 20 gauge?