I am thinking of getting an AR-15. I've never had one before. I am an avid deer hunter and have had several bolt guns, semi-auto hunting rifles, and lots of shotguns. I will use the rifle mainly for plinking and shooting stuff around my property - hogs, paper plates, old campers, etc. At some point I would get a new upper for deer hunting (from reading tons of posts on here I think you can put different barrel assemblies on the same lower?). I need some suggestions on what to purchase. Keep in mind I am new to AR's and do not understand what A-2, A-4, M-4, or any of that other stuff is.