Recurve crossbow, Compound crossbow & Pistol crossbow

Evidence suggest that the crossbow originated in China during the 4th century BC, though a type of crossbow called the gastraphetes may have been independently invented in Greece at about the same period. It wasn't until the 10th or 11th centuries AD that the crossbow became a significant military weapon in Europe. It passed from general military service in the 16th century, but its use for hunting and target shooting has continued to the present day.
The Chu-ko-nu is equipped with a magazine which holds 10 steel-tipped bolts, about 5/16' in diameter and 7.25' long, which it shoots in succession. It is operated by grasping the handle of its stock in the left hand and working the lever with the right, the piece being held just above waist level and being steadied solely by the grip of the two hands on the handles, as with a pair of large garden shears.
The crossbow played an important role in the late Medieval period. The crossbow was really the first hand-held weapon that could be used by an untrained soldier to injure or kill a knight in plate armour. The most powerful crossbows could penetrate armour and kill at 200 yards. Crossbows are easier to aim than longbows because the crossbowman doesn't have to use a hand to hold the string back while aiming. On a similar note, a crossbow can be loaded long before the bowman might need to shoot. In this way, the bowman would be able to shoot immediately if surprised. Crossbows require less upper body strength to operate as well. One can use both arms to span (draw back) a crossbow. Crossbows do, of course, come with a price. That price is in efficiency and in the firing rate. Efficiency is a more technical problem.

No bow is perfectly efficient, but Medieval crossbows were particularly inefficient. The reason for this is that the draw length and the lathe (also called a prod) of crossbows are short. So even though a crossbow may have a great deal of stored energy when spanned, the tips of the lathe do not have enough time to reach the maximum velocity, so the amount of stored energy is not transferred fully to the bolt. It is the lathe tip velocity that determines the speed of the bolt that is loosed. This problem could have been alleviated with a longer draw length or a longer lath, but that would increase the weight and bulkiness of the crossbow, which are already two distinct disadvantages of the Medieval crossbow.

CROSSBOW USES (War, Sport and the Sinister)
Crossbows were mainly either weapons of war or sport (hunting and target shooting). Of these, most were probably weapons of war. The larger war crossbows were used to defend fortifications. Smaller crossbows (~4 ft.) could be quite effective in open battle when used correctly though. Since a crossbowman is particularly vulnerable while reloading the crossbow, he requires some sort of defence (a wall or a shield) to be effective in battle.

Though popular sporting items, crossbows were very expensive, and only the wealthy could afford them. Crossbows were often highly prized by assassins. There are a number of laws that address this problem in particular. Assassins would be the main users of the smallest crossbows, as they are more easily hidden and transported.

WORKING MEDIEVAL CROSSBOWS (what they tell us)
There are working examples of Medieval crossbows, and from them we can get a good feel for the range and power they had. Throughout the Medieval Period though, crossbows became more powerful. Sir Ralph Payne-Gallwey loosed a bolt from an actual Medieval crossbow spanned with a cranequin and achieve a cast of 490 yards. The ordinary 15th. century crossbow would likely cast a bolt 370- 380 yards. These crossbows would surely outperform almost any longbow in terms of distance, but the accuracy of the crossbow at those ranges would likely be poor at best. At point blank range, the crossbow almost certainly had very high penetrating power.

MATERIALS
The crossbow was probably introduced into Europe circa 900 CE, and possibly a couple of hundred years earlier. From this time until the 12th. century, the prods of crossbows were self-bows, or made out of one piece of wood. Composite prods, made out of horn and/or sinew (tendon) and/or wood were introduced to Europe in the 12th. century. The composite bow was the technology of the Saracens, and was a marked improvement over the wood bow. Steel prods were made and used after 1350 CE. The tiller of each type crossbow was usually wood, though was sometimes also composite. Self and composite crossbows usually employed a bridle made of rope or sinew to attach the prod to the tiller. With this type of method, the prod is essentially just tied onto the tiller. This method was occasionally used for steel prods, though they were more often held within the tiller itself, rather than lashed to the end of it.
The nut of almost all types of crossbows was often made of horn.

CROSSBOW DESIGNS - History:

As mentioned in other sections, the crossbow's earliest widespread use was probably in China, during the 3rd century B.C. or earlier. On single-shot crossbows, one type of latch/trigger mechanism was a very clever precision bronze casting with three moving parts and no springs. Surviving wooden stocks end in a type of pistol grip. Their laths were either of composite construction or made from multiple bamboo slats bound like an automobile leaf spring.

Another type of crossbow used by the Chinese since at least 210 B.C. was a repeating design with a gravity-fed box magazine! The magazine was situated above the bolt track. When the lever at the rear of the crossbow was first raised and then lowered, the box moved forward, caught the string in a wooden recess and drew it to full cock, dropped a bolt into the track and released the string. These crossbows were neither powerful nor accurate, but they could launch a bolt every second or two until the magazine emptied. Poison was usually smeared on the points to increase their lethality.

In the manner of handbows of the same period, early Western crossbows featured wood laths and long power strokes (compared to later examples.) The most common latch mechanism was a rotating nut of bone, ivory or antler. To achieve greater power, massive 'composite' laths made from sinew, horn or baleen, and wood came into use; these were shorter and much stiffer than earlier wood laths. As draw weights increased, new methods and devices for spanning had to be employed, which included the cord and pulley, belt claw, 'goat's foot', bending lever, cranequin and windlass. Steel laths later provided even greater power. Spanning devices made reloading a slow process compared with hand bows. Crossbows were more useful for hunting and siegecraft than in open battle, where their slow rate of fire was a serious handicap.

Features usually found on military and hunting crossbows of the 14th to 16th centuries include a fairly plain, straight stock, a sinew bridle binding the lath to the stock, a cylindrical latch nut and a long iron trigger. It would have either a simple rest or a grooved track to guide the bolt; a stirrup, cocking ring, or cocking lugs would be present depending on which cocking device was to be used. The stock could be held in the same manner as a firearm, or rested on top of the shoulder and the trigger manipulated with the thumb. The bolt's point usually served as the front sight when aiming.

Sporting crossbows of the 17th to 19th centuries were used for formal target competitions and hunting. Aperture sights and set triggers were usually present on target crossbows. Bow irons and similar fittings for securing the lath replaced the sinew bridle. Bullet crossbows became popular for small game hunting and informal target shooting, using a double bowstring with a leather pouch to launch a lead, clay or stone balls. The barrelled crossbow or slurbow also shot round balls, using a conventional bowstring and a tubular barrel. The range of features found on sporting crossbows of this period is better seen than described; the books by Payne-Gallwey, Stevens, Bilson, Heath and Paterson listed earlier include illustrations.

The crossbow was (and in some cases still is) a popular hunting weapon in Southern Asia and parts of Africa. The construction used in both areas is similar in that a relatively weak wood lath is mounted to a straight stock with a bolt track. The latch is simply a notch in the stock; the trigger is a peg that is pushes the string out of the notch from below. On some examples, the stock is horizontally split for part of its length, so that pressing the two halves together pushes the trigger peg upward. Since bolts from these crossbows have little kinetic energy, they are invariably poisoned. Bolts are slivers of hardwood or bamboo, usually with simple leaf fletchings.

Crossbows of medieval and renaissance design were very inefficient devices. Modern tests indicate that armour-piercing bolts, while heavier than war arrows, achieved about the same velocity (130-40 fps) from a 700 lb. draw crossbow as an arrow did from a 80 lb. draw longbow. The initial velocity imparted to a crossbow bolt is governed by the velocity of the bow tips as the bolt and string part company. Despite their heavy draw weights, medieval laths were too massive to accelerate rapidly. This was made worse by short draw lengths, which reduced the time available for the tips to accelerate. In addition, the massive bowstrings required for such heavy draw weights robbed energy from the bolt. Balanced against these faults is the higher ballistic coefficient of the short, heavy crossbow bolt, as compared with an arrow. This meant that crossbows often could shoot further and hit harder than hand bows.

Modern hunting crossbows are engineered to launch 400+ grain bolts at initial velocities in excess of 200 fps, with draw weights of about 150 lbs. This provides ample kinetic energy for big game hunting with a far lower draw weight than would be the case with a medieval crossbow of similar power. A longer power stroke coupled with a less massive fibreglass lath makes the difference.

Modern target competition with the crossbow falls into two quite different classes. In international 10 meter competition, shooters use a crossbow that marries the elaborate stock and sights of a smallbore target rifle with a short-draw steel lath. The draw weight is well over 100 lbs., so cocking is performed using a long steel bending lever. Bolts are about 6' long and made of unfletched wood; their metal points are threaded like a coarse woodscrew to facilitate removal from the lead plates used as backstops. Field crossbow competition takes place at 30, 40 and 50 yards, with bolts similar to those used in hunting. Because lighter-drawing field target crossbows are shot over greater distances than in international 10 meter, their stocks and sights must be suited to a broader range of adjustments. Field target crossbows are usually hand-made, often home-made by their users.

GLOSSARY

Note: Some of the terminology preferences used in this list are the author's and not common modern usage. Crossbow terminology is not altogether standardized and one should not be too pedantic about it.

Crossbows and the Law