|This article is about an older version of DF.|
Dwarves or other creatures armed with crossbows deal "pierce" damage from a long distance. A Dwarf Crossbowman, or marksdwarf, will usually open fire at a distance of 20 tiles or so from their target, but a bolt may carry 30 or more*. While also doing decent general damage, a bolt does a fine job at piercing the internal organs of a creature, which can possibly cause organ failure and instant death, unconsciousness or crippling of any size target. This is of limited use against creatures without internal organs, such as magma men. Occasionally a bolt will get stuck in a target; the only known use for this is that a wrestling dwarf may grab the bolt and twist it in the wound.
A marksdwarf who is forced into melee will use the hammerdwarf skill to bash enemies with their crossbow. If you'd prefer your marksdwarves to reload instead of going into melee combat, you can go the ilitary menu, iew their squad, and then toggle to tell them to stay close to their station. This will cause them to go and collect bolts, then start shooting again, instead of either standing in place because they don't have a path to the enemy, or running out to smack the enemy with their crossbow.
Immigrating marksdwarves bring their own crossbows and 30-40 bolts. Immigrating trappers often arrive with Novice Marksdwarf skill, though will only bring a crossbow and bolts if they also have ambusher skill.
Increasing Crossbowman skill requires firing upon a target (hitting is not required), with "live targets" granting much more experience than an archery target. The difference is huge, on the order of ~67 bolts fired (~7.5 experience/shot) in practice vs 17 bolts fired (30 experience/shot) against live enemies to achieve novice rank. Higher skill grants better accuracy and higher rate of fire. An archery range is only used by military dwarves that are off duty, and they will only use wood or bone bolts during practice.
Training marksdwarves can lead to a number of problems. Marksdwarves only train with bone or wood bolts. They need individual archery ranges of adequate size (3 tiles minimum) set up. Any activated military will only practice if they are "standing down" (not "on duty"), which can be toggled only in the ilitary screen, and then by iewing any member within a squad and giving that squad orders - the entire squad will have the same orders, whether that squad has 1 dwarf or dozens.
Marksdwarves will not equip bolts and practice (or fight) with bolts if they are carrying items in hand (as checked via iew nventory). Items get in hand if the marksdwarf has been wrestling, a frequent Cross-training exercise.