"How to load precision ammo" could be the topic of a Ph.D thesis. There are many ways to skin this cat and much disagreement about the "best" way to reload. The tutorials on here are a nice starting point, but I agree with mijp5 that many of the steps are low yield. Experiment and do what works for you. Having the right tools and making precise, repeatable measurements is 90% of the battle. Instead of trusting a single measurement, make many measurements and then use the mean of your distribution. Tools like comparators are inexpensive and critical for making length measurements. Annealing is also a critical component to reducing ES. Luckily when you use Lapua brass you can skip many of the brass prep steps. I don't do anything to Lapua brass except size, load, shoot, anneal, and repeat.