Now that I no longer have any Ruger 45 Colts, I don't have any bore dimension data for it. However, I always bought 0,454 to 0,457 diameter soft lead bullets/balls for my smallest grouping BP and nitro loads in that Ruger. 0,452s just did not shoot as well as 0,454s, for whatever reason, with one striking exception, some 300 grainers loaded over plenty of H110. Could have been other reasons, such as the common oversize Ruger 45 Colt chambers, etc.
I always thought that any nominal 0,452 bores on 45 Colts had as much to do with size of widely available 45 Colt mantled bullets as with any manufacturing benefits -- compare with existence of 0,357 and 0,355 for "38s" and 9mm.
Now that cheap military surplus ammo is scarce, or less, I wonder just what is appeal of dual cylinder 45 Colt/45ACP? If one wants to load a smaller case than 45 Colt, 45 S&W has long been available and works really well for this. Of course, folks having a bunch of 45ACPs and loading tools, etc., 45ACP in revolver would make lots of sense.