depends on your chamber, every time a reamer is sharpened it gets smaller, so takes less powder in a tighter chamber to make the same mv. I don't pay much attention to manuals except the charge weights. if I'm not making the mv that its supposed to I keep upping the charge till I either get there or have signs of high pressure, then back it off till its safe. faster twists make less velocity at the same pressure as does cut rifling vs. button rifling, the manual is just a guide, the numbers are not etched in stone.
RR