Sure there is, the transition from chamber to throat area is plainly visible. It's going to be a ramp, not a sharp shoulder, but the change in diameter is there.


If you have a sufficiently accurate measuring device such as calipers or pin gages, you will find that the back end of the chambers measure about .483 and the front end will measure about .459. At least that's what my rechambered .455 measures, although on mine the backside of the cylinder was faced off, as opposed to the recoil shield on yours being thinned.

The most certain way to be sure though is to get a Letter of Authenticity from Roy Jinks, S&W Historian. But I'll bet you a nickel that your gun was originally chambered in .455, not .45 Colt.

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