If you want the very best brass for accuracy and reloading longevity in the 455, making cases from 45 Colt, 45 Schofield, etc. is the way to go.
When I had a S&W mkII 455, I found that after thinning the rims in a lathe (or drill press), I could determine the best overall length to get the case mouth within .010" of the chamber throats. What I ended up with was a case whose overall length was ideal for my revolver, yet didn't coincide with any commercial cartridge.
Back then, my 455 was used as my first centerfire target revolver for Bullseye club matches. The cases were the first problem to solve. Then, I needed to cast my own bullets. I found an old Lyman 45 swc mold that dropped slugs at .455"-.456" depending on my alloy.
Finally, an "old school" 45 Colt size die helped ensure my cases weren't overly resized. That will ruin your cast bullets when you seat them, and eat into your case life.
By the way, I never could stand those stubby mkII cases, especially Fiocchi! Cases were expensive, yet case life was poor. And, I found that the ones with small primer pockets (Fiocchi) didn't group as well.
For off the shelf cases, the best I found were Canadian made Dominion 455 Colt cases. The "455 Colt" is longer than the 45 ACP but shorter than the "Long" Colt. I'd have to check my notebook to recall the exact length.
Enjoy! They are great revolvers!
Jim
