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I have to say, one of your statements has got to be incorrect. Bullets fly in a slight arch, but can be considered a straight line. It can't be dead on at 75 yards, and in the next 25 go berzerk. Honestly, sounds like the shooter needing more practice if I had to guess. (I have this problem too!) You are really confident at a certain range, you shoot well. Try to push it, and you lose your confidence and concentration.
just my 2 cents