Yes, 6mm Benchrest is the cartridge for my benchrest rifle. I used Lapua brass because it's the best but also the most expensive. If you can make it last, it becomes some of the cheapest.
THe rifle is a savage 12 benchrest with a Shilen barrel bedded with devcon. 6mmbr is a great cartridge for absolute accuracy out to 600 yards and there was a website and forum dedicated to 6mmbr. They since changed to https://www.accurateshooter.com/ check it out. You can find the answers you are looking for there, but beware. Benchrest shooters will do things for the tiniest accuracy advantage (real or imagined)
I got a bench rest rifle to experiment with loading to see what i could accomplish, accuracy wise. It was a fun experience. I learned that you got to have a good platform to start with. I learned how to bed a action/barrel. I learned that you have to have a custom hand lapped barrel. The best production barrel can't come close. I learned that consistency is everything. EVERYTHING! I learned that match grade is a word that gets thrown around a lot but doesn't mean anything.
Further down the rabbit hole I got?

Haha, nah
Yeah, I've read good things about Lapua brass. Thanks to an awesomely cool 2a member, I have Lapua brass for my .308.
I did some reading of at accurateshooter website. IF (or when) get around to building a custom gun top to bottom, I have a lot of good info. Understood on the benchrest shooter things. I'm not into benchrest shooting, but had read some about it. Like any other forum, there's bickering amongst groups and benchrest vs PRS vs hunters seems to be a common one. Nothing against any, just different interests and priorities. Similar to one of my shooting buddies. He's all about hunting, so light gun, light barrel, etc. He poopoos on me and another buddy with our heavier profile barrels, heavier stock or chassis, etc. To me, all good. Just fun to be shooting.
Understand what you are saying about the experiment. Good to know what a platform is capable of. I am nowhere near that, but I'm an experienced enough shooter to at least suspect when equipment is hindering. Like that damn Hogue stock on my Rem 700. But along those lines, it's amazing at stuff like quality of scales, calipers, etc that folks get into. I'm not spending over $500 on a scale! But then I'll spend $$$ on glass though. Haha