@cajun makes a lot of sense!Starting with good brass makes a big difference. To get that level of consistency your going to need to pay attention to neck tension. Thats going to lead to turning necks and using a bushing die to get the exact tension on all your rounds. A hand seating die and an arbour press so you can tell when a bullet seats easier or harder and use for a sighter. A good way of measuring your powder charge. Your going to have to anneal the brass at some point or it all changes. And of course a rifle and a shooter capable of such and a load your rifle likes.
@ajkellerusmc what you are talking about is starting to get into BR accuracy which takes more than case prep imo!
There are plenty of articles out there to read if this is where you want to go
Copyright © 2003 Precision Shooting Magazine. Reprinted by permission, all rights reserved. Preparing Cases for Long-Range Accuracy by Jacob Gottfredson I have always been a little amazed that loads with relatively large velocity spread...
You have to remember that with trying to squeeze every ounce of accuracy there is so much more that is needed not just basic case prep some of which come with specialised equipment.
Weight sorting cases
Control neck tension with bushing dies
Be able to measure concentricity of a loaded round
& then you have to be able to dispense powder more accurately than what most dispensers will do with a variance of less than a 10th of a grain.
When all that is said & done then the rifle & shooter then needs to be capable as well.