Amateurs practice until they get it right, Professionals practice until they cannot get it wrong. Using a Data book is the tool of professionals, winners, best of the best, wiether you buy a Storm or Impact or make your own, RECORD your shots, be honest, even if its a bad day of shooting, I see BR shooters doing it, F-Class shooters doing it, and of course Sniper wanna be's like me doing it, record your shots, I guarantee it will make you a much better shooter, at first it seems pointless, over the years I look over the data I recorded and can see the things I did right, and way wrong. Along with a data book I recommend a chronograph and a Krestral 4000 or better, with these 3 items all the important items can be recorded.