I started loading about 1979. Nobody ran around with technical question about COAL. Most people didn't even have a dial caliper! We took a factory round that functioned in our pistols and used it to adjust our dies to. The IMPORTANT thing is, If the bullet has a canalure adjust the bullet depth so the case mouth and the canalure are lined up after whatever crimp you use. With 9mm, this should be a taper crimp.
Then the crimp need to be tight, but don't cut into or crush the bullet. Running a finger nail over the edge of the seated bullet, you will feel the case mouth, you need to, this is where the case headspaces in the chamber. (again, reference a factory round)
The two reasons the loading manuals give you OAL/COAL is to let you know where this particular bullet fits and the chamber pressure is safe at this length. If you play with the COAL much you MAY need to adjust the powder load. But that usually only happens at the top and bottom end of the listed loads. If you are using a load from a manual, X.X grains of XYZ powder, any of those rounds that fits in your gun will be safe in you gun. It is when you confuse the wrong component that you run into trouble. So read and re read the listings!