Hey guys, new to the board so please bare with me.

My brother brought his new 50 cal. Omega over today to sight it in and we had no problem getting it dead on at 100 yds. We then went out to 150 yds and with two shots it shot about 8 inches low and about 6 inches right on both shots. He is shooting 295 grain power belts with 3-50 grain pellets and Winchester primers. This gun should shoot a lot better than this, what could be going on guys?? We made sure to run a brush down the barrel between shots so I would not think that this should have been the problem.