DNS109, With one known exception, .454" bullets are too large for any Ruger 45 Colt. Why? If cylinder throats are at the optimum diameter of .4525" the largest bullet that will fit is a .452". Anything larger presents two issues ... the first being the cartridge will not fully chamber. The second being .... anytime a bullet is larger than throat diameter, chamber pressure will increase dramatically. The exception is a Hornady "cowboy" bullet. These bullets are very soft (BHN 10) and have a knurled body. When loaded in a normal 45 Colt case, the knurling literally "irons out", resulting in a true .452" diameter.
Prior to 1951, revolvers chambered for 45 Colt typically had .454" bores and cylinder throats. S&W petitioned SAAMI to change the bore diameter for 45 Colts to .451" so bullets could be compatible between 45 ACP and 45 Colt in their Mod 25 revolvers. Ruger Blackhawks were made after 1951 so they all have .451" bores. There are still some foreign made Colt clones with .454" bores but mostly, .454" bullets are the standard for nearly all 45 cal rifles.