The cylinder chamber throat size determines what size bullets to use.
Many new .45 Colts have over-size throats.
If .454" bullets fit the throats with a tight slip fit, that's what you need to use, regardless of bore size.
If .452" bullets fit the throats, that's what you need to use.
However it will do no good to pick a .454" bullet because that's what the bore slugs, if you have .452" throats.
Because those .454" bullets will be sized to .452" when you shoot them through the .452" throats anyway.
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