I use a chronograph and other signs to determine general pressure vincinity.
If I have to decrease oal to achieve desired function: reduce charge and work back up using the chronograph and other signs such as spent shell location as my guide.
I rarely use the exact combo found in the book. I would say 99% of the time, my components differ from theirs in some aspect.
That is regarding auto pistols.
Revolvers using canullured bullets: seat to the cannulure. Pretty simple there.
Rifles: determine ogive touching rifling, back off 30 thou, and start powder work up. Unless the book tells me how long the leade is in their test barrel, the books oal is again meaningless to me. Their velocity data is very helpful however, since I can compare theirs with mine, and use some other tricks, such as bolt lift and such, to give me a general idea of the pressure the load is generating.
sudo passwd root is my Sig using the Tapatalk android app and is inserted automatically. It allows you to change the root account password in a Linux distro, if you have admin privlidges.
sudo passwd root