I was using the 180 grain and 190 grain Hornadys with a stiff charge of IMR 4831 for years in my 300's. WLRM primers, neck sized brass, fireformed, and outstanding accuracy. The interlocks kill a moose, bear, or elk with authority. They gave me sub moa. all of the time. I also used a stiff charge of H 4831, with the same results, but a little less velocity. I also use the interlocks in my Weatherby calibers with outstanding results. IMO, if Norma loads them in the factory Weatherby rounds, then they can't be a bad bullet. It has to be fairly tough to withstand impact velocities that Weatherbys can develop. I am wondering about the bedding job on your 77. Most of them shoot rather well. Good luck on your endevour.