Just to take a step back here, a few things are getting muddled in the question.
deadkitty wrote:I have been trying to keep my cartridge length close to maximum in an effort to get maximum reloads out of each case, but I've noticed the trim length in the ADI reloading manual varies per projectile.
Where did you read ADI provide different
trim lengths for the same same cartridge with different projectiles? You sure you don't mean
COAL is different with different projectiles?
deadkitty wrote:I 've been keeping my coal below the max (2.254-2.256) am I doing this right?, or should I be following the trim lengths suggested?.
You'll know some of this but lets just get a few fundamentals clear from the get go.
Trim length is the length an empty case should be trimmed to. There is no 1 exact length that is 'correct'. There is safe range which is between the trim length (minimum), and a maximum length. A case must be trimmed before exceeding this length. These numbers are firm, don't go outside of them.
COAL is the 'cartridge over all length'. The length of a cartridge loaded with a projectile.
You are right here that the COAL length does vary with different projectiles, this is because different shape projectiles will be difference distances from the rifling depending on the shape of the bullet if the COAL of both cartridges is the same.
Read this post by Aster (has pictures instead of my typing a long explanation) -
How Vital/Dangerous is out of spec COLDo you follow?