I have had revolvers lock up with the start load. Some guns just dont like some components.

Temperature also can make a difference with some powders. A load worked up in cold temps can be over pressure when it is 95 degrees out.

Generally, the bullet makers loads would be correct. I have some 124gr 9mm bullets and I found loads of 5.0 gr max and 6.2 gr max of Unique. Also big variation in COL. I use the bullet makers load.