alt Hacker Newsnot a gunsmith, but cast iron manages to be both soft and brittle at the same time. and the barrel and bearing parts would have to be machined anyways. you have to try to harden it too. its probably easier to just machine the whole thing out of decent quality steel. just guessing.
really? they didn't have machining in the 1700s. how about a good'ol musket? or a bit more modern: a gatling gun. I always thought those were made under coarse conditions. I mean, people just need something that makes a spark against gun powder,goes boom and shoots really fast projectiles. If a shotgun is possible, then an automatic shotgun doesn't feel like it's a stretch. I would think the firing mechanisms might not be tolerant of amateur techniques, but the reloading and trigger parts at least might be. I'm also not a gunsmith, no idea what I'm talking about for the record.