i am a dummy in my haste to get ready for a tactical shotgun course i purchased a brand new still in the box 870 express magnum. ok it had everything you could want for a tactical course, synthetic stock, rifle sights, 20" barrel, black gunkote type finish etc..etc. i open the box and guess what it has a fully rifled barrel no good for my purpose, but perhaps its what you always wanted. so i want to trade this brand new never even had a shell in it, 20" fully rifled barrel with rifle sights for a new or like new 20" or 18.5" smoothbore barrel with either rifle sights or a picatinny/weaver rail on it. i think its called a cantilever mount. help me out if you can i really want to attend this course and i am now broke i cant just go buy another barrel.