If you have a bad neighbor a fence probably won't help much.
1. Game camera's ( evidence he's on your property, but don't forget to erase the video if he picks up some lead. )
2. Regular target practice( if he thinks your a bad shot he might stay even further away.)
3. A couple of Rottweiler's trained to stay on the property with an invisible fence.

There never seems to be a cheap solution.
Last resort buy him out.