Yeah, the Berger manual seems to be a little conservative. Do you know what barrel length powder they were using for the RUM data? Most guys I see loading the RUM with 210 Bergers and Retumbo are getting in the 3100-3150 range in a 26" barrel. Nosler's online manual shows 3050 with 210 partitions which have a longer bearing surface using RL25 out of a 24" barrel. Not sure why any bullet or powder manufacturer would ever use a 24" barrel for RUM testing?
The standard 300 WSM powders do produce velocities in the 2950-3000 fps range for 180 bullets. But RL17 really does well in the WSM case and gives me 200 fps more velocity than H4350 with the same pressure. I suspect it will do well in your SS also.
I don't mean to detract from your thread but I thought I would give a little more perspective on the comparison.
Carry on with the good work
Berger manual 26" highest velocity 2945' with H870.......Rich