I'd keep the 3-9 X 40 Nikon and forget the BSA. Why would you need a 6 X 18 scope on the .308? The "cheaper" Nikon's (Prostaff, Buckmasters, Team Primos, etc.) are quite good and a good value to boot. If you get much above 10 X you're probably going to have to get an A.O. model, and the glass quality (on cheapos) usually disappoints.