If you are shooting instinctively, and getting good groups at ten & twelve, then you are doing something right. It may be as simple as not bringing your focus and concentration to the same level as you back up farther from the target.
Example: If you are shooting at a three inch bullseye at ten yds and hitting it, put a 1/2 "
black dot in the center of the bullseye and shoot at the black dot from ten yds. You will probably see an improvement even at ten yds. Now as you back up,keep that same level of concentration on that tiny black spot. You cant shoot at the bullseye, you have to shoot at a spot on the bullseye. The more you are able to focus and concentrate on a speck, the tighter your groups will be.(providing your form is consistent)
When shooting at game if you shoot for the kill zone you will probably shoot high. If you shoot at a hair, you will be dragging home meat.
If it was easy it wouldn`t be fun.