DAA you said overall legnth is no good to use. I dont understand why not.
I go though the process of sooting a bullet in a dummy, fired cartridge, chambering the round then checking it to see if it has contacted the lands just like Ronald described. When there is no more contact I then use this cartridge as my base for OAL when using that particular bullet. A different bullet will require a different OAL measurement.
If all the bullets of one certain type including the weight are all made the same, why couldn't OAL be used?