You can build a portable long range target with a used bed sheet and a couple of aluminum 6 foot stakes. You build pockets on each end of the sheet and stretch the sheet between the stakes, then drive the stakes into the ground. Then glue butcher paper to the sheet to get a stiffening. Spray a large orange or black dot in the center, and you can then tell what your rifle is actually doing at various distances. Also, follow eric1115's advice and get a steady, solid rest as a firing position. Sandbag both the stock in front of the action and the buttstock in. The only things touching the rifle should be the sandbags, your shooting hand, your cheek and your shoulder(place your non-firing arm on the rest or ground and place your non-firing hand at the buttstock to help steady it on the sandbag: don't use that hand for supporting the stock, just as a steadying help-let the sandbag support the weight of the buttstock). Make sure your elbow is rested. If you have a good rest, your crosshairs shouldn't move at all except with your heart beat. (natural point of aim):You should be able to look through your scope and have it centered on the target, and then close your eyes and open them and still be within 1 moa of center on the target with your crosshairs (actually, it should be less than about 0.5moa). Fire two 5 round groups at 400 yards as a base of accuracy, then move the target at 50 yard increments and do the same thing. This will tell you if its the rifle, the loads or you. It will also give you data on actual bullet drop at various distances with your rifle at your altitude. You'll want to keep a data book with that information for future reference. Keep in mind that this will give you data for that load only. If you want exact data for another bullet/load, you'll have to do it again. But you will have a baseline to work from and it will not require more than maybe adjusting at 400yards and 600 yards.