Many years ago in another lifetime I was in the Air Force and we did our qualification on a 1000 inch range. The targets were cutout silhouette targets, just like the big kneeling "E" tagets except these were probably about 12 inches high.
The appearance at 1000 inches was the same as a standard silhouette target at 100 yards. It worked fine for open sights and I still do some shooting at this range. Saves a lot of walking downrange changing targets.
If that's all you have, make the best of it. Not everyone has a perfect place to shoot. That's why I moved to New Mexico and bought some acreage-- to have a place to shoot.

