Back in the early '70s, I only owned two cartridge handguns: a Ruger Blackhawk in .45 Colt and a Webley MK IV in .455. Don't know how I did it, but I was able to deepseat SWC bullets in .45 Colt brass and fire these in the Webley, using reduced powder loads, of course. I guess the headspace was a little slack at the caseheads.

Later, I found loaded CIL .455 ammo and used .45 ACP dies to reload the round.

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John 3:16
WAR EAGLE!