Congrats and welcome to the 300 Ultra club! I'm shooting the SS 700 and had a brake installed. Cut the recoil in half and makes shooting at the range enjoyable (At least for me, haha). (Take the brake off hunting). I haven't had the luck you've had with the factory loads. Can't find anything that'll group great like yours seems to. I have worked up a couple loads using the new Nosler Accubond in 180gr and Sierra 165gr HPBT Gameking. The 165's will cut a jagged hold off the bench. What I have discovered in my rifle is, it really doesn't like the hot loads and does much better on the low end of the scale. Can't explain it, but I've proven it with every load/bullet I've loaded. Happy Shooting!