You beat Phil and I to getting around to making a post.
Seems like a reasonable dwarven alternative to crossbows/arbalests. Flair for culture is nothing to shame. I would argue that it should take 4 (load, charge, aim, fire) emotes rather then 3 (load + charge, aim, fire) for balance purposes and to align with what is shown on the loading procedure. Further a runic steam pressured weapon should also be unable to be prepared in advance beyond the first emote as you would likely run the weapon at too high of a pressure causing it to explode (serious maiming of wielder).