John,
I missed your post somehow.
Anyway you're right, my rifle is different. My factory 700 has a long throat and I'm not anywhere near the lands with a 150 stuck in the case very much at all. I don't have my data in front of me right now, but I know for sure I'm not getting near the velocities you've listed with 15 and 4895 despite using the same components and amounts.
I can't recall my Lapua based numbers, but in RP hulls I know I'm nearly 200 fps short of what you're showing with 46 of 15.
Dave
