You probably have not ever really wondered about nocks, but why not? There are many different kinds of nocks out there in terms of shape as well as material and it is actually quite critical that you use the right one for your crossbow! There are also even some nocks that are illuminated to help with the tracking of arrow flight as well.
So what are the different shapes of nocks?
Crossbow arrow nocks can typically be divided into 4 main categories, the flat, moon, capture and what we would call a hybrid moon nock. Most manufacturers will have a specific nock shape they recommend, or even require for their crossbow.
The flat nock.
The flat nock is the oldest of the nock designs and is also the most simple. It is, as its name would suggest, just a flat disk on the back of a crossbow arrow. It allows for the placement of the arrow in just about any configuration on the arrow track and allows for slight vertical movements of the string when firing.
The moon nock.
Also commonly called the half-moon nock, the moon nock has a slight concave curvature to the nock. This allows the crossbow string to have a depression in which to rest to better ensure the string does not slip above or below the arrow during firing. The moon nock is mounted in such a way that you can only load an arrow with a vane pointing straight down or straight up. Most crossbows that utilize the moon nock will have you load the arrow with the vane straight down in the groove of the barrel.
The capture nock.
The capture nock is a deeper variant of the moon nock. This will be a familiar nock to those shooters that have used compound vertical bows as the nock has a deeper groove that actually snaps onto the serving of the bow string. Like the moon nock, the arrow will be seated with a vane in the vertical position either pointed straight up or straight down. Also like the moon nock, most crossbows that utilize a capture nock will have the vane pointed straight down when loaded.
The hybrid moon nock.
This is the newest of the crossbow nocks and is essentially a moon nock but with concave cutouts every 120° on the nock. Essentially when you look at it, you will note that it fits on the string like a moon nock, but unlike a moon nock, you can mount the arrow to the string in multiple vane configurations like the flat nock. This allows you more freedom in how you string the arrow if you have a trackless or barrelless crossbow design (think whisker biscuit).
What are nocks made of and why does it matter?
Crossbow nocks are typically made from either plastic or aluminum. For most low power crossbows, the material is not that critical. Where it becomes important is when you begin to step up to the hyper velocity crossbows that are starting to become more common. In order to achieve high speeds, there is a tremendous amount of pressure that is unleashed when the trigger is pulled. This force is imparted on the arrow nock by the string and can cause plastic to shatter if not properly designed to handle this force. Many high powered crossbow manufacturers recommend nocks be made from aluminum for this very reason.
What are lighted nocks and why are they used?
There are many manufacturers that make illuminated nocks for use with crossbows. These are basically just plastic nocks that do not look any different when mounted on an arrow. When the arrow is fired, however, a small piston or other actuator causes the nock to light up with an LED that allows you to visually track the flight path of your arrow. For a better visual picture, think of a tracer round fired from a gun. This can be useful both to determine where an arrow impacts your game as well as for finding an arrow following a miss or a pass through.
As you look at the variety of nocks that are out there in today’s market, you really want to pay attention to what the manufacturer recommends. There is usually a good reason for their recommendation beyond simply wanting to sell you their arrow. Always be sure to ask questions to ensure whatever nock you are purchasing is suitable for your particular crossbow. Having a nock fail can create a nasty situation as it can result in your crossbow dry firing, which can then create damage to the crossbow or to the shooter, neither of which is desirable!