Just thought I would put that out there, doing an archive search lots of people ask what to use but usually not a lot of real answers. And the couple answers that I've found usually say theirs measures to .452.
I was surprised by this so I slugged it twice, got .453 both times. And I verified my nice Mitutoyo digital with a bunch of different pin guages I have for measuring cylinder throats, it read correctly from .357 to .452, so my calipers seem to be accurate.
Have to say I am a wee bit disappointed, that's a bit on the outer acceptability of generous. Oh well, guess it's old style .454 lead boolits for me