I've only been reloading for my newly acquired 300wsm for a short while and have loaded and shot about 125 rounds, most cronographed .
So far my highest MV was a 3120 average with 180's and RL-17 out of a 24" Tikka.
IMR-4831 was second fastest, but more accurate than RL-17 turning in a average MV of 3050 and my most accurate load over 3000MV. Today I shot a lighter load of IMR-4831 at about 100fps slower at a MV of 2950, but was more accurate. To date my most accurate loads occurred at a MV between 2750 and 2950.
With your longer barrel you should be able to reach book max, but that doesn't mean it will be your most accurate loading. I actually attained a MV AV of way over 3100 using a book max of RL17 but had definite pressure signs and only mediocre accuracy, so I ended up pulling the remaining reloads. Funny thing was the previous load using RL-17 was only 1 grain less and showed no pressure signs.