Can't get achievement Bullseye.

When I go to the achievements page. I choose to do the achievement Bullseye. I make the target. Shoot the middle from 31 blocks away. Doesn't work. I try to shoot it in the middle in close range. Doesn't work. I don't know what to do next. I wasted 73 arrows doing it over and over again. Doesn't work. Can you help!!!!???