Post interrupted by Forgotten Beast 504, so some of this has been covered already by others, but I'm way too lazy to completely re-type the post.Actually crossbows can be quite simple. A bow, a cross piece, and lever on a pivot that holds back the string is all that is needed. I mean the Chinese have been using them for some two and half millennium (and still do in some police forces). The problem is with the idea of the cranequinn/windlass based late medieval crossbows.
My suggestion, without any real knowledge of what is possible via raws, would be have a couple different versions like the orcs have with bows. So a simple wooden (or bone) crossbow would be relatively weak, but easy to use, and fairly quick to reload/fire. A more advanced crossbow using a composite wood+bone+sinew (Maybe leather in DF?) prod (bow-arms) + a mechanism might be still fairly easy (early?) to make but have better penetration but take a little longer to reload. Then you've got your repeating crossbows already in. Lastly you might add the full steel (metal at least) prods, cranked windlass, heavy crossbow for even more late game penetration, at the cost of fire-rate. Of course I'm not sure how much control you have over fire rate aside from maybe weapon weight so I guess that's a toss-up for balancing. The complexity of the reaction should work just as well.
I simply have the feeling that most people make crossbows, and ignore all other ranged weapons.
The problem here is that it's a hassle to manage all the different ranged weapons and ammo types. You need separate squads for each weapon type otherwise they grab the wrong ammo and muck things up. There just aren't enough dorfs to fill out, or benefits from, outfitting a squad each of javelineers, axe chuckers, and hammer tossers. At least as compared with the relative simplicity of a combined arms melee squad. Standardizing equipment simplifies logistics too much to not simply pick the NATO 5.56 bolts. Unless maybe you're up to your neck in the not-so-dead, then you might standardize around the 20x102mm DU throwing hammer instead.
Maybe, you could strip out those other weapons, and only use one "throwing arm" weapon for all of the axe, javelin, hammer ammo. Of course that would make the melee attack questionable. Plus, I'm not sure that I would want to risk military trained throwers losing comrades and embedding ☼Shale Mug☼ in their fellow dorfs in fits of pique. Of course: "Urist McOne-lung has been ecstatic lately. Urist McOne-lung was hit by a flying object recentely. Urist McOne-lung acquired masterfully crafted Shale Mug recently. Urist McOne-lung was grievously wounded recently. Urist McOne-lung admired own Masterfully-crafted Shale Mug lately. Urist McOne-lung is having trouble breathing," does rather epitomize FUN.
!!Anthropology!! Dwarfs use crossbows. If you are a 4.5' stunty who likes to run around confined spaces the relatively flat trajectory of a crossbow is ideal. Trying to swing a sling and hitting a too near wall is not on the wind-up is not. Trying to use
archery with a bow in a 6-7' high mineshaft is likewise not. Having a natural inclination toward mechanics is bonus. Guns are good too though ricochets are potentially be problematic.
