I thought I'd reply again with the facts from your post just to arrange my thoughts better and confirm some information./w3tcompact/icons/smile.gif
<font color=blue>We've met and talked a couple times. </font color=blue>
This guy is not a complete stranger.
<font color=blue>...he's firing a high powered rifle</font color=blue>
Not a .22, not a shotgun, a rifle.
<font color=blue>...into a target on a hay bale</font color=blue>
<font color=red>What size hay bale? A big round one?</font color=red> Even if it's a big round one, if he's firing at a target (and he's any good), the bullets hitting repeatedly in almost the same location will, eventually, create a little 'tunnel' where there's almost no hay, or anything else to stop the bullet. Even if he's shooting at a paper target with multiple bullseyes on it, there will be areas where there's concentrated impact areas. Even if he has a plate steel backstop (we had this in our basement shooting range when I was a kid), I don't think he should be firing towards dwellings.
<font color=blue>...on our common property line.</font color=blue>
It may not be directly at your house but he is definitely not firing in the opposite direction, either.
<font color=blue>This goes on for 70 - 80 shots over the next hour.</font color=blue>
More than one shot every minute. Hmm, makes me wonder what this guy is doing. Sighting in a scope? That's a lot of shots to sight in one scope. Perhaps sighting in the scope on a number of different rifles? Testing different hand loads in the same rifle?
<font color=blue>The downfield trajectory of this firing position bisects my property, running about 100 feet east of my house.</font color=blue>
So, as you look out at this hay bale, it's just slightly off to one side of your house and he's is firing in your direction. This isn't good. <font color=red>How far away is he? Why can't he fire in some other direction?</font color=red>
<font color=blue>This means I'm pinned down, unless I'm willing to accept this guy's feeling that he would never miss, there will never be a ricochet, and a hay bale is an adequate backstop for rifle fire.</font color=blue>
This is what I would nicely tell the guy.
<font color=blue>I talk to other neighbors - they state he does this "all the time"...</font color=blue>
I would want to confirm this myself by asking the guy directly. 'All the time' can mean different things to different people.
<font color=blue>They shake their head when they say this.</font color=blue>
Does this mean they have talked to the guy and had a bad experience? Called the cops on him? Didn't talk to him and just complain to each other?
<font color=blue>and is a "gunsmith". </font color=blue>
I would think a gunsmith would know how to safely handle a weapon and shooting towards a building, occupied or not, doesn't strike me as safe.
<font color=blue>I'm a little worried about getting on the wrong side of the "gunsmith", especially since we're not in the house on a full time basis, and he has a gun. </font color=blue>
Understandable concern, but it might be jumping the gun (sorry, bad pun /w3tcompact/icons/eyes.gif) a little. Having said that, you are already on the 'wrong side' of his target.
<font color=blue>What is the proper "rural living" approach to this situation? </font color=blue>
Actually, the same approach if you're in the city in an apartment...Talk to the guy, find out what he's doing, i.e., don't completely trust the neighbors information, tell him the effect he had on your family and see if things can be worked out.