I've shot some lighter trail boss loads through my Encore .500 and had the same issue, way too high. I was surprised as I figured the lighter load would group lower. I've been sticking with the hotter loads, mine really likes 2400 with the 300gr Hornady FTX bullets. Nice rifle, short, light, powerful, and accurate.
I did switch to a smaller, twilight apperature on the rear sight, which I found helped out my group consistency.