It was hard to decide where this thread should go as it is related to at least two categories.
A few years ago, I picked up a three barreled hand cannon from an antiques seller here in Korea. It was made (or converted) for percussion cap. I can tell you that it is a heavy beast, although I haven't weighed it. I also never measured it and didn't think about doing it today (it's at our Korean traditional house, which we only visit once in a while), but I did take a few pics.
Looking on YouTube, I see someone else has one and touched it off: