According to Vetron's Guide to Weapons and Armour, the crossbow has a "10" effectiveness rating.
Now here is a real missile weapon. The impact of the crossbow will stop a rampaging troll. The crossbow is traditionally made of mahogany with carved maple veneer on the sides depicting Lord British's device, the Silver Serpent. A favorite among Bards for the singing of the crossbow's string.
Made from strong and resilient yew, bows, and their stronger counterparts, crossbows, make formidable long-range weapons. Be aware, however, that one engaged in hand-to-hand combat is unlikely to be able to load such a weapon, much less shoot it.
Bows and crossbows are capable of firing with tremendous force, but they require use of both hands and cannot be used effectively at point blank range.