The compound bow revolutionized archery by multiplying input energy over distance. It stores the power of taught cables and limbs in a mechanical system that allows shooters to hold a full draw without tiring, and then propel an arrow to a target at speeds up to 340 feet per second.

The basic components of a compound bow are two pulleys with equal radius connected by an axle. When the larger pulley moves, it pulls its rope a longer distance than the smaller pulley. Because the archer applies an equal amount of force to both, that equal amount of energy is applied over a shorter distance. That shorter distance is the difference between the limbs at full draw and the string at a let-off, which can be up to 90% of the bow’s total draw weight.

Compound bows are also able to store much more energy than traditional longbows or recurves because they have limbs that are bent at both ends and have cams that create a larger gear ratio for the bow’s cable system. This allows a greater percentage of the bow’s draw weight to be transferred into the limbs and a longer, more powerful limb that can then be released with much less force.

The limbs are attached to the bow’s riser by limb bolts. These are adjustable with standard allen wrenches to tighten or loosen the limbs’ “draw weight,” which is the maximum amount of force required to reach full draw. This adjustment must be made carefully so that the limbs are not pulled to such a degree that they break under the strain of a released arrow.

A compound bow’s frame — called the riser — holds the bow’s sights, stabilizers and quiver. It is typically made of aluminum or magnesium alloy and either forged or machined. It must be rigid enough to resist warping or breaking but light enough to be as compact as possible. It must also support the limbs and cams, which must be rigid and strong enough to transfer stored energy into an arrow (speeds can exceed 340 feet per second) without breaking under the tension of the string or cables.

Compared to the relatively simple construction of recurve bows, compounds are far more complex and expensive to manufacture. That, plus increased component costs, has resulted in a price jump from last year’s $1,099 Mathews V3X to this year’s Phase 4 at $1,299.

Another factor is the compound’s greater potential for torque, or twisting, during shooting. This can cause left-right errors and a plucked or snatched release that can make it more difficult to maintain a steady anchor point and aim accurately. The good news is that most manufacturers now design their bows to have limb pockets and cams that are more forgiving of these torque problems than in the past, but it’s still important to select a bow with plenty of mechanical adjustment for your personal fit. A bow that’s too short or too tall can easily damage the limbs, cables and release system.