I've shot my Trapdoor Springfields out to 1,000 yards with my cast bullet loads with good success. The military sights make it very doable, particularly with the 1879 sights on the rifles made prior to 1884. The Buffington sight on the 1884 and the 1888 rifles is very adjustable and repeatable in deflection, but I've just never got along well with it.
Elevation settings are easy as long as you know the trajectory of your load. I duplicate both the 1873 45/70/405 load and the 1884 45/70/500 loads. The 1879 sights are calibrated for the former and Buffington sights track with the 500 grain load well. Wind deflection is the big bugaboo and when you're used to shooting a 30-caliber match rifle at 1,000 yards, the difference between a modern round and the old war horse in deflection is quite eye opening.