Concerning the topic of the Minie ball. I just came across a reference to the "Nessler Ball" (or bullet). Apparently during the mid-1850s, this was a sort of minie ball for *smoothbore*(!) muskets. And was said to extend the effective range of muskets considerably. It's description sounds like a short minie ball. It was popular with European armies, especially in the 1850s, as a stop-gap measure, but for some reason was never adopted by the US during the Civil War. Here's a link to some more info:
http://www.civilwarguns.com/9910b.html
Can't seem to find out too much info about it, but that article mentions a test. If anybody knows anything else, I would be interested to hear.