PSA Grendels - some reports an curiousness - barrels seem to get more accurate w/ age

[FLshooter]

The problem with budget barrels as they require a lot of break-in.Time and ammo cost money..quality barrels shoot well out the box. But if what I read is correct ,that you are getting 1.2 moa with wolf steel cased ammo,you should be able to tighten your groups w/quality brass cased ammo.
What brass cases ammo,if any ,have you already tried?