T.C.,
That might depend on what you consider "miniature"... If you're talking about a smaller Longrifle for a child, I don't think it would be half size. Rather something with a shorter barrel and length of pull.
If you're talking about a true miniature, there was one at Dixon's this past summer that was about 6" long. The Gentleman who made it escapes me at the moment, maybe some of the other guys here know what/who I'm referring to? I think Acer or someone also did a link at some point. Increadable work...
Ed