Barnes recommends .050 off the lands as a starting point. My friend in Montana used some Barnes in his 340 Weatherby mag and he said that he did .050 off the lands and they shot great also. He didn't try changing it. All I have changed is powders and weights. I started with 88 grs. to 93.5 grs but it was hot out and I started getting too much mirage so I couldn't shoot the 93 and 93.5 gr loads.
I am going to load up some more and chrono them.
Heres my 338 RUM with a 30" barrel on a Savage action. Shoots pretty good with 99 grains of US 869 and 300gr SMKS. Chronograph has them going a touch over 2800. Hodgdon list the max load for US 869 as the same for the Lapua and the RUM.
GREAT LOOKING RIFLE, thats a great group at 100 yds for such a cannon. Your brake and stock are really cool. I am shooting 250 gr SMK's and GK's and will try Accubonds, would they still recommend .050 off the lands?????