I have this friend (No, really, it's true) who has a Ruger Blackhawk Convertible 4 5/8's bbl in .45 Colt with an ACP cylinder. Does anyone know, or have an opinion they can defend, whether the ACP cylinder could be used in a different .45 Colt Blackhawk? Specifically he's looking to buy a 7 1/2 inch in .45 Colt, with no ACP cylinder. D'ya think he could use the ACP cylinder from the 4 5/8's BH in the 7 1/2?