For those that think that because they haven't heard of a problem it doesn't exist:
The short version: SAAMI pressure for 455 Webley is 13200. SAAMI pressure for 45 ACP is 19000. Every standard 45 ACP is like shooting a proof load of 455.
If you have a 455 that's been converted, only shoot VERY light 45 ACP loads with LEAD bullets in it.