I have a 4x EER Leupold on my .454 Encore. I was a little perplexed sighting it in, I would be dead on at 25, but 3-4" high at 50. It has to do with the muzzle jump, the slower the load, the higher the impact, the faster the load, the lower the impact because the bullet is subject to less muzzle jump due to higher velocity. That's how it was explained to me anyhow, feel free to disagree. All I know is that with a 320 gr. cast GC and 27 gr. H110, I can hold dead on an oil bottle anywhere from 10 to 100 yds. and be pretty sure to hit it, gallon jugs are not even a question. Hope you enjoy your barrel, don't ignore the light loads in the .45 Colt class, they are a lot of fun for practice out to 50-75 yds. or so. If you want to compare data, let me know. That 320 load is running at 1600 fps...
SElmer