Just wondering how many others have guns that just love a certain bullet, too where powder charge has little to do with its accuracy?
Well, it was one of the reasons many of us BR shooters hand swaged our own bullets to better match our barrels/bores/throats, and to improve on the weight, jacket variations and concentrics.
I've seen numerous rifles dislike various brands, weights, styles, etc, and then they became great shooters with others. In the "old days", we saw this a lot with some of our club target/varmint rifles, and usually, if they would not shoot a Sierra match bullet well, they were ready for a rebarrel.
Different bullets, brands and even lots can have varying diameters that better or worse fit a throat and/or bore size. Years ago, we miked a lot of Hornady .30 cal 168gr Match bullets that came in at .3073-.3078", and the competing Sierras came in at .3085-.3089. Many of our match M1's, M1A's, 700 Varmint 308's, etc preferred the larger Sierras. However, a few shooters' rifles with tighter bores had a slight preference the Hornady's.
Its one reason many shooters once, and some still do, slug their bores to determine proper bullet fit.
Edit to add) I saw a couple of older 30 cal rifles with overly large bores that would only shoot well when loaded with .303 cal, .311" bullets, and those bullets made those old rifles work for hunting for many years.