I have the Gen I sendero in 300 RUM. The only thing I have done with it is I bedded it and put on a Holland QD muzzle brake
(recoil was getting up there with the 208 Amaxs). I initially found a good load with 94 grains Retumbo and the 208 amaxs, but after the bed job and the muzzle brake install, I think the harmonics changed, and the Amax never shot as well. I never found an acceptable load with the 200 gr Accubonds. They never seemed to shoot better than MOA. I am currently testing the 225 grain Hornady match bullets. I have a load I may stick with; 87 grains Retumbo, federal 215 primer, COL 3.650"( Max so I can still fit them in the magazine) approx MV 2820. It is consistently giving me .5 MOA out to 300 meters. Once I can get to the 1000 meter range, I'll verify it for long range. I know some are pushing it faster, but groups opened up and pressure signs were showing with more than 87 grains. I want this as a hunting load and need to find out how this bullet's terminal performance is on larger game i.e. Elk. Good luck.