Are you shooting from the same rest at 50 as you at 100, are the targets at the same height? Sometimes if you place a stock on sandbags or worse, a hard surface, the stock will bounce all over the place with the recoil, throwing your shots off. If you think its a mental game, try shooting your .22 at 100, if you don' t have one, think about investing in one, it will pay for itself in cheap practice and its a very cheap way to refine your shooting from different positions such as standing. I usually fire off 3-400 rounds with the .22 at 100 yards before I even pick up a centerfire everytime I go to the range. Hope this helps.