My Burris Fullfield was dead on out to 300 yards and only off about 3" at 500 with my 270 load.
This was at my home in PA and on a muley/antelope hunt in WY. I took an antelope at 325 yards allowing for about 12" of wind drift and a muley at 437 yards in dead calm air both with a single shot.
But I practiced out to 500 yards all summer and did some final tweaking just before I went on the hunt.