Crossbows vs. Compound Bows

Crossbows and compound bows are two tools used for hunting and archery. Both use string tension to propel a projectile, but their similarities stop there.

Crossbows consist of a bow mounted on a stock that shoots arrow-like objects, called bolts or quarrels, which are shorter and denser than arrows. On the stock is a device that holds the bowstring when it is drawn. A trigger system made of iron or steel holds the string in the nut to keep the force of the pulled string and to shoot the user must release the nut, which will release the string and shoot the quarrel. The line the bolt follows as well as the discharge of the crossbow is very similar to a rifle because the line of travel is flat and straight, much like a bullet, rather than arched or bowed as an arrow shot from a bow. Users also aim and shoot the crossbow very much like a rifle, placing the crossbow in front of the body and aiming.

The bow part of the crossbow, or the prod, is very short when compared to other bows; this results in a much shorter draw length and a much heavier draw weight—how far back the shooter must pull the strings back and how difficult it is to pull. This is significant because it is essential that the same amount of energy be stored in the short strings of a crossbow as there is in the longer strings of a compound bow to make an accurate and quality shot.

There are many variations of the modern crossbow. A recurve crossbow has tips that face away from the shooter and the bent limbs are longer, resulting in a longer draw length and more acceleration to the bolt with less hand shock to the shooter. Recurve limbs transfer the strain of the draw and shot on the bow materials but can be noisier than other crossbows.

Compound crossbows are similar in design to compound bows. These crossbows have very stiff limbs making them use energy better than other crossbows, but the rigidity is excessive; hunters and archers cannot draw it back simply by pulling an attached string. They must use pulley systems to capture the maximum amount of available energy from their comparatively short draw lengths. Aiming and shooting a compound bow is much like a longbow or recurve bow; users pull the bow across the body and aim parallel with the steadying arm.
Compound bows use the same pulley system as compound crossbows, but provide users with “let off” relief. These bows use a levering system of cables and cams to bend their stiff limbs. As with the compound crossbows, having a great deal of limb rigidity makes the bow more energy efficient but it simultaneously sacrifices simple design. Again, the limbs are too rigid to pull back with a string attached directly to them; these bows have another string attached to the cams. The shooter attaches a wrist pull to the eyelet on the pull string. Each cam, or wheel, has one or more cables attached to its opposite limb. When the archer or hunter draws back, the string turns the cams; the cams pull the cables, and the limbs bend down, storing more energy.

The levering system has a draw-force curve that peaks and then lets off to a more manageable holding weight. “Let off” describes what happens when a cam rolls all the way over, taking a percentage of that drawback weight off the shooter. For instance, if a hunter has a compound set at 65 pounds, the shooter must be able to pull back 65 pounds of pressure on the string before the system kicks in, holding part of that weight. The bow might have a 65% let off, so the hunter only must hold a little over 42 pounds of pressure while waiting to take a shot. This is useful because it lets the shooter have more force than available through a recurve or longbow.
Many states allow the leisure use of these weapons for as well as target shooting; always check local laws before using a bow or other firearm. Make sure to use sound safety practices, and have fun!