I did some mroe shooting today to test performance with the 375 Ruger with 260 Accubonds and RL17. I started by loading up 3 loads at charge weights in half grain increments from 83 grains to 84.5 grains. I was pleased with the velocity I gained over H4350 in a comparable load. I was also pleased with how well RL17 fills the case. My results are below. I will post target pics later.
All loads were loaded with CCI 250 primers in Hornady brass loaded to a COAL of 3.350
83.0 grains 2835 fps 1" group, 2 touching
83.5 grains 2880 fps .75" accuracy
84.0 grains 2915 fps .35" accuracy all 3 touching
84.5 grains 2930 fps 1.5" group
I didn't get any pressure signs or hard bolt lift, but judging by the chrony readings and and the opening of the group the 84.5 grain load is approaching max in this rifle.