The largest issue I see is the nature of the weapon itself. As a cudgel, the point of the thing is to hit stuff with it with enough force to damage the target. If you put a barrel in the middle of it, then it is invariably going to bend after enough use. That could cause it to violently backfire. Now, ES does have some unnaturally strong metals, like ebony, but they are expensive, hence the scalability issue. Morphing the design into a blade instead of a cudgel would likely negate that issue, since it wouldn't stress the barrel as much, but you would end up with a weapon that is less effective at range than a bow, and more clumsy than a normal sword due to the excess weight. Being the first version, that is to be expected, though in reality, gun swords were a thing that never really took off, apart from bayonets.