I'm building a 6.5/.284 on a model 70 winchester with a 28" Shilen select match barrel with a 1 in 8 inch twist and pla n on shooting 120-140 grain bullets.#7 contour by the way. it is topped off by a leupold 8.5 x 25x50mm with leupold rings and bases.I'm planning on hunting whitetails out to 500 yards if it proves to be accurate and punch paper out to possibly 800 yards. after load developement i plan for premier reticle to install dial in turrets to match the load/bullet. now for the question: Do I need special base's to be able to shoot these distances, or will standard leupold bases of a certain height work? sorry for the length but was trying to give you a feel for my needs. thanks timbo