i've seen videos of other prop gun conversions firing before (
http://www.youtube.com/watch?v=4cOeqD80gzY), so that was the level of gunsmithing/craftsmanship i was thinking of when i asked about a conversion kit earlier, in case people were thinking i was going to get out the sheet metal and hot glue and about to slap them onto a working gun or something... i value my limbs and digits, and i wholeheartedly believe in letting professionals do the dangerous work.

i've seen conversion kits for firearms sold online, and they all say that they are to be installed by a gunsmith (like changing components of an old mosin nagant rifle to be more modern).
sorry for the delayed reply - i was offline all weekend. offline and NOT blowing my hand off, mind you.