Re: 257 Weatherby Mag
My best loads shoot less than MOA out to 300 yards. My best luck has been with Hornady Interlock and Barnes Triple Shok in 117 - 120 grain bullets. I tried a number of different powders and settled on RL-22. Just speaking from memory, but my Hornady bullet load is 3300 fps and my Barnes load is a litttle over the top at over 3500 fps.
257 is my go to rifle for 90% of my hunting. You will enjoy it. MJ
Prayer, planning, preperation, perseverence, proper procedure, and positive attitude, positively prevents poor performance.