Just my 2 cents, if your groups are good at 50 yards, then if your groups open up at 100, it may be because you can not hold the same as with the longer distance. I try to sight in the smallest target that I can see at 100. If you are shooting at a large target and it is black there is no way of knowing if you are remaining constant. Try putting a dot on a blank piece of paper, the size of a dime then go from there, if you can see it with your scope fine, if not go to a Quarter size dot. This has helped me as being 70 the old eyes ain't what they use to be. If my groups are VG at 50 and not so good at 100, I never blame the gun or the load I blame myself. Lou