I've actually been kicking the idea for a realistic and
period-appropriate gunpowder mod around for a while. Here's the gist of it:
* Eight lumps of brimstone + two lumps of saltpetre + one bar/block of coke + fuel = ten bars/blocks of gunpowder, which has appropriate matgloss to make it
very flammable and with a high material value; about equal to iron, perhaps?
* One bar/block of gunpowder + a hundred
metal bolts or arrows + one bolt of cloth + one reel of thread = one hundred
metal 'rockets' in four stacks of 25. These would deal about 250 PIERCE damage.
* The actual guns would be based on the
hand cannon, and be about twice as heavy as crossbows, but have the [CAN_STONE] tag, since real-life examples of cannon carved out of stone aren't completely unheard of. For that matter, you could carve a serviceable one out of wood if you had to, though it'd wear out quickly.
In summary, guns would offer a significant but not
quite game-breaking edge in ranged combat, but a steady supply of ammunition for them would require a strong economy unless you happened to embark somewhere with brimstone. The workings of the actual gun are as close to real-life as I can get within the limitations of .40d, and I'm putting this one on the back burner until the new version arrives.