I'll get right down to it. I bought a Weatherby Vanguard in .338 WinMag. Had a professional mount and boresight the scope, a Nikon Buckmaster. I used Leupold dual dove tail mounts/bases. I was shooting/sighting in this weekend. It was holding 3/4 moa. I shot 40 rounds. At about 33 rounds it started shooting about 12 inches low and six inches right. Then it went down hill...still on the paper, but North East South and West....I was shooting off a led sled, I am not a new shooter, and I am not recoil sensitive....any thoughts? Could it just be from shooting quite a few rounds and heating the gun up? I shot 40 shots in about 2 hours. I'm pretty frustrated....any help would be awesome! Thanks a ton.