No real answer for you, just some thoughts.
A year or so ago there was talk that a group was planning to put together a 1000 yd. range uparound Horseshoe Bend. You might ask Cliff (at the Ponderosa Gun and Amish Quilt store in the link) or the guys who are hanging around the LongbranchSaloon on 55. They had some land scoped out and were talking about putting in a public facility.
It is my understanding that there was a thousand yard shoot somewhere down aroundBlacks Creek a couple of years ago. Maybe a bit further out where thatshotgun range is located?Chuck Mawhinney, one of the top5 snipers from the Vietnam era, was there and you can find pictures on the Internet if you look a little.
There has to be somewhere the Boise PDguys (see article link) and National Guard units go to practice under these conditions, I am guessing/suspecting thatmaybe the Guard Training Area out Vista Road has a spot where they can do an ad hoc setup for 1000 with a suitable backstop?