I've heard of MV maxing out, but haven't experienced it myself. Are you seeing any signs of excessive pressure: bolt face impressions on the base, popped primers, stuck cases, etc.?
Based on my Barnes and Lee manuals, the hot powders for 160-175 gr bullets in this caliber seem to be RL25, Magnum, H870, IMR7828 and Accurate 8700. The first two should get you to 3100 fps with those Berger 168 gr bullets.
FWIW, I don't invest as much in a single powder on my first pass as you did. I usually shoot a string of increasing charge, but only one load per charge weight. I repeat this for at least two more powders. When I shoot these strings, I look primarily for MV and pressure signs. I also watch impacts to identify the high and low positions.
Then I select a couple of powders and develop loads for 5-shot groups, each group with a different charge. I usually only shoot 4-6 such groups on the second pass, looking primarily at group extreme spreads. I usually find what I'm looking for without needing a third pass. If not, I then start to vary seating depth, change powders, or change bullets.
Last edited by bruce_ventura; 11-27-2011 at 08:35 AM.