Resurrecting this thread from last year. On Cabela's there's an interesting review of the pepperbox:
"I enjoy collecting percussion revolvers and this one really captured my attention for a possible Cowboy Action Shooting side-match shooter. In case you are interested, this basic Colt Navy frame, when the 3-inch cylinder is removed, will receive a .36/.44 standard cylinder and .36/.44 barrel assembly, making this a convertible firearm. This revolver is an attention-getter among black powder enthusiasts, and also a truly manageable handgun in action."
So if you have an old pietta brass frame colt navy that's getting some frame stretch, this might be your answer.