The best of the .455/.45 Colt conversions were done by deepening the chamber AND cutting a rim counterbore at the rear without shortening the cylinder. These guns will still fire the .455 without difficulty, as its rim is somewhat larger than the Colt, and using the counterbore preserves the .455's headspace. The ACP/AR conversions are usually shaved, and no longer handle the .455.
Larry
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