I've inherited a nice older model Remington 1100 that's right now is fitted with a 12 gauge barrel. When I inherited it the person gave me 3 barrels one of em is a 20 gauge barrel and another is a 16. You can't simply change the gauge of a shotgun by changing its barrel can you? Would a different gauge barrel even fit properly? I'd hate to mistake it for a 12 gauge and have the receiver portion of it actually be for 16 or 20.