I have a Remington 870 Wingmaster that my Grandma recently gave me after my Grandpa passed away. This gun is most likely from the early 80's since I dont recall my Granpa ever hunting. It is a 12 gauge 2 3/4" Camber w/ a fixed mod. choke. My questions are....First, would it be safe to shoot steel BB shells w/ this barrel for the rare occasion that I go Goose or Duck hunting? Also, is it possible for me to change the barrel to a 3" model that I can switch chokes on? I know that I can remove the barrel, etc. I just didnt know if the receiver had anything to do with shell size. Thanks in advance for any advice.