I've seen manufactures printing tables on targets and on ammo boxes; never been impressed.
You have to start somewhere. Nothing is going to be perfect but using the target I mentioned, or ballistic tables probably wont be right on, but they will get you on paper.
There are environmental concerns, I agree, that is why score/data books are so critical. One should record every shot fired, in what conditions, what changes were made,.........everything. That will give you history/data so you can make the corrections needed the next time you shoot.