These guys build them. Scroll down to the bottom of the home page just above the counter and read the black print.
http://www.smokelessmuzzleloading.com/I have read about a few guys having them done and one guy has a .45 that is quite the tackdriver shooting very fast for a muzzleloader. If I run into him again, I'll try to get some information.
But to answer your question, Yes they have been done before. Wouldn't it be cool if Ruger would come out with a factory version that didn't cost an arm and a leg? :wink:
