That all depends. As above state, manuals are for their bullets only. The big differences between the bullets have to do with skin friction (how the bullet contacts the case and the barrel) If you have two JHP's which are the same weight, and also the same material, which are of the same dimensions, then you shouldn't have a problem.
Bullets like the barnes TSX's have less surface area contact, therefor less skin friction, and therefor less amount of psi generated to push them down the barrel. Same thing with coated bullets, less skin friction=less psi.
If you use moly coated bullet data for a non coated bullet of the exact same weight and diameter, the non coated is going to generate much more pressure than the coated bullet. Some of these differences according to the manufacturer are 2 grains or more. The differences between lead bullets and copper coateds are even greater.
If I have a bullet which I don't have the exact data for, then I will check a bullet which is VERY similar in the books I have, make sure I get more than one source, and even triple check on somewhere like hodgdon.com to make sure I'm not going over a stated maximum.