And further on Bart B's points, I have a standard recipe for 69gr match bullets in .223 using Varget and CCI primers. The load has worked in at least 5 different barrels (3 on my rifle, 2 on my dad's) plus is pretty similar to what any number of other shooters will be using if they are using 69gr match bullets. I can also replicate that performance with Alliant RL-15 and Remington primers.
So while I will agree no two are the same there are many recipes that are "known" factors in many calibers. It gives you a good place of reference to start if nothing else.
NRA Master, Highpower Rifle, Across-the-Course
NRA Expert, Highpower Rifle, Mid-Range Prone