Crossbow Components Explained

Parker CrossbowI thought that explaining what the essential components of a crossbow are and how they all work together to make a crossbow function would a good starting point for the “newbie” or beginning x-bow hunter. Without the knowledge of what each component is, you most likely would have a hard time following along while reading other articles or discussing topics on the forum. I certainly don’t want anyone to get lost with the terminology that surrounds the crossbow , so we’ll take a look at all of the major parts. By the end of this article, you’ll have a much better understanding of what each component is, and how they all form to create a crossbow.

The Bow:
It would be impossible to have a crossbow without having a bow. The bow is the power station of a crossbow. Without some type of bow, there would be nothing to propel the arrow. The bow of a crossbow can be configured in two arrangements. The first type of arrangement is referred to as a recurve bow. It consists of a riser, two limbs, and a string. The second type of bow is referred to as a compound style bow. This consists of a riser, two limbs, two wheels mounted at the end of each limb often referred to as cams, a string, and two cables. We’ll take a much deeper look into both types of bows in the next article so at this point, I won’t discuss the way they each one work, or the advantages and disadvantages of each one in this chapter. The bow of a crossbow is mounted horizontally and can either be attached to the very front of the rail or on reverse draw technology crossbows, it can be mounted in the middle or further back on the barrel or rail.
The draw weight of your bow is the amount of force, measured in pounds, that it takes to compress the limbs of your bow, based on the manufacturers specifications. It is a universal measurement with both the recurve and compound bows. Most hunting crossbows will have a draw weight of at least 125 pounds with some of the recurve models climbing up into the 275 pound range. The draw weight of the bow on your crossbow usually is a direct indication of the type of speed one can expect from a particular model. In general terms, the heavier the draw weight your bow is, the faster your arrow will be. That would hold true if all crossbows were made equal, but there are two other key factors that can directly effect how fast your bow will shoot an arrow.
Besides the overall draw weight of your bow, the power stroke of the bow is an equally important factor when relating to a crossbows efficiency in propelling an arrow. The power stroke is the distance the string will travel from the point where the bow is at rest, to the point when the bow is in its cocked position. As a rule, the longer the power stroke, the more time the bow will have to transfer energy to the arrow, thus producing a faster arrow. For those of you that are familiar with vertical bows, the power stroke of a crossbow is just like the draw length of a vertical bow. The reason the limbs of a crossbow need to be so much heavier than that of a vertical bow is because the power stroke of a crossbow can be more than half as short as most vertical bows.
So why don’t crossbow manufactures just make a longer power stroke on all crossbows and lighten the peak draw weight? Well for starters, crossbows tend to be a bit front heavy because of the bow being mounted so far out front of where you hold the fore grip of the stock. Having a longer power stroke would result in moving the bow even further out in front of this point making it very hard to aim a offhand and decreasing the overall hunt ability of the crossbow. Some manufactures have found a way to extend the length of the power stroke without making the overall length of the crossbow longer by doing what is referred to a bull pupping the trigger. We’ll talk more about the bull pup trigger design in the trigger section. For now, just know that a bull pup trigger design allows for a manufacturer to have a longer power stroke, but not without a negative side effect.
The one way to effectively extend the power stroke of a bow, and actually increase its balance is by using the reverse draw technology method. With a reverse draw technology crossbow, because the riser of the bow is mounted behind the string, it allows for the string to be pushed farther down the barrel increasing the overall power stroke without lengthening the overall length of the crossbow. And because you are transferring the weight of the bow itself towards the middle of the crossbow, the crossbow becomes less front heavy, as a result, balancing out the bow better.
The cams on a bow is the third factor that can effect the amount of energy that is transferred to the arrow, effecting arrow speed. Especially the shape of the cam. A cam can be completely round or can be oblong like an oval or an egg. Altering the shape of the cams will change what is know as the draw force curve of a bow. The draw force curve is a measurement of a bows draw weight at a particular point in the power stroke. With a recurve bow, the draw force curve is generally a straight line on an upward angle. It starts off at a certain point when the bow is at rest and increases uniformly when the bow is drawn. For each inch the bow is drawn the poundage increases by a certain amount. With a compound bow, depending on the shape of the cams, you can manipulate the draw force curve so that you can increase the draw weight of the limbs rapidly over a shorter distance in the power stroke and then achieve and hold the peak draw weight of the limbs for a given distance and then let the bow relax back to a lighter poundage. It is this change in draw force that makes a compound bow more efficient than a recurve bow. This is why you will see many compound crossbows with a shorter overall power stroke and lighter overall draw weights than recurve crossbows. Depending on how aggressive the engineers designed the cams for your bow, will determine how aggressive your draw force curve will be and how much energy will be transferred to the arrow.
As you can see, there is a lot of variables that go into the design of a bow for a crossbow. The ultimate goal for any manufacturer will be making one that is safe and reliable, while still pushing the edge of performance.

The Barrel, Track, or Rail:
Connecting the bow to the stock of the crossbow is the barrel. The barrel is often referred to as the “rail” or the “track”. At the time of this article, currently all crossbows have some type of barrel or rail except for one. We will focus on the types of crossbows that do have a barrel, since chances are your bow most likely has one.
The barrel can be made of two types of materials. On many of the lower end or entry level crossbows, you will find a plastic barrel that is incorporated into the stock. They are injection molded together as one piece. Many will have some sort of stiffening rod inserted lengthwise to add rigidity and help maintain straightness. The second type of barrel is an aluminum barrel. Today, most crossbows will have an aluminum extrusion used as a barrel. Aluminum is light and strong, and stays straight. The aluminum extrusions are smoother and and less abrasive than the plastic barrels. You’ll find these types of barrels on your higher end bows. There is a third type of barrel that one manufacturer is now offering and that is a carbon barrel. The advantage of the carbon barrel is that it is very light. So it will eliminate some of the overall weight of your bow. Because working with carbon materials is relatively new to the crossbow industry, there is a hefty premium for choosing a crossbow with a carbon rail.
With any of the above mentioned types of crossbow barrels, you’ll find a groove down the center of it which guides the arrow and allows the downward facing vane or fletching (often called the “cock” vane) to ride through barrel without interference.

The Riser:
The riser of a crossbow is the section of material that the limbs mounts to. A riser can be made from cast aluminum or magnesium, machined aluminum, and to date one manufacturer is offering a riser constructed from carbon fiber. There are many configurations of the crossbow riser. Some are very simple in design and relatively small in size. While others can be an engineering work of art and focal point of the bow. In the end, the main purpose of the riser is to hold each limb of the bow together at a particular angle.

The Foot Stirrup:
The foot stirrup of a crossbow is a hoop looking piece of metal material at the very front of a crossbow. It is usually mounted to the end of the rail or riser. The foot stirrups main function is for inserting a foot so that you can stand on the front of the bow to put down pressure on it while cocking the crossbow. Another job of the foot stirrup is to act as a guard for protecting your arrow when there is an arrow loaded in your bow. Every manufacturer designs their crossbows so that a few inches of arrow will stick out past the end of the rail. The foot stirrup actually protects the end of the arrow, especially one tipped with a broadhead, from being knocked around while hunting. To reduce some of the harmonic noise that a foot stirrup can make after shooting a crossbow, some manufactures coat them in rubber. This helps reduce any vibration that is transferred to the stirrup from the bow after the shot.

The Trigger and Safety:
The trigger is responsible for telling your crossbow when to fire the arrow. There are many designs when it comes to the crossbow trigger, but they all have one thing in common. That is, to release the string when pulled. Some triggers are very good with a clean crisp break with little to no creep. While some manufacturers offer triggers with a lot of travel. Unlike a gun trigger that only needs to hold back a firing pin, the crossbow trigger is designed to hold back much more weight. Sometime even 275 pounds or more. So designing a trigger that has a light pull to it while still being safe can be a challenge for manufactures. My personal opinion is that some manufacturers are pushing the limits of how light a trigger should be. Sometimes, in the heat of the moment in a hunting situation, when a hunters excitement level is at a level that is unattainable during a practice session, having a trigger that is too light can spell disaster. Especially on those long winter sits when your fingers and hands can go numb.
The crossbow trigger mechanism comes in two basic designs. The first design is the standard way where the trigger is located directly underneath the latch that holds the string back in the cocked position. The second type is called a “bull pup” trigger design. With the bull pup trigger design, the string latch is mounted behind the trigger and then connected internally with linkage to the trigger. By doing this, manufacturers can lengthen the power stroke of a bow without lengthening the over all length of the crossbow. There is one trade off though. The bull pup trigger design will take up some of the room needed to rest your face on the stock. It also pushes the sight bridge of a crossbow further back. As a result, to be able to see through your scope correctly, often times you must lean your head back away from the crossbow and because the bull pup design has already taken up some of the room on your stock, you aren’t left with very much stock for your face to get a good cheek weld.
The safety works hand in hand with the trigger. Just like a gun, your safety prevents your trigger from being pulled by accident or before you intend it to be. Every crossbow will have a safety. Most of the bows will have an auto engaging safety that will automatically move to the safe position when you cock your bow. There are however a few manufacturers that do not have an auto engaging safety. If you end up purchasing one of these brands, you must manually put the safety into the safe position after the bow is cocked. Even on the crossbows that do offer the auto engaging safety, it is a good habit to check that the safety is in the safe position after cocking the bow and before loading an arrow into it. Some safety designs allow for the safety to be operated while having your hand remain on the grip and others require you taking your hand away from the grip to operate. Either style will work and it really comes down to a personal preference of which one you like over another. Chances are, if you really like one brand of crossbow over another, you will be stuck using the safety that is offered by that particular manufacturer.

Anti Dry-Fire Prohibitors:
Most modern crossbows come with some sort of device to eliminate the risk of dry firing. A dry fire is the result of shooting a crossbow without an arrow loaded into it. This can cause serious damage to your bow and possibly cause an injury to you or any other nearby person. So most manufacturers include an extra safety mechanism that will not let the bow fire unless an arrow is loaded. While each manufacturer may have their own design, there are a few main types of these prohibitors.
The first type truly is an anti dry-fire. That means that without an arrow properly loaded into your crossbow, the bow will not release the string when the trigger is pulled even with the safety in the fire position. I would consider these types of dry fire prohibitors as true anti dry fire mechanisms. The next type is what I would consider an anti dry fire prohibitor. What makes these different from the anti dry fire mechanisms is that they will actually let the string be released from the trigger mechanism when the trigger is pulled. Then a stand alone mechanism, not tied directly to the trigger actually catches the string within a very short distance, not allowing your bow to completely fire. And yet another type prevents the safety of your crossbow from even being moved into the fire position unless an arrow has been loaded into your bow.
As of the time this article was written, I only know of two recurve manufacturers that do not include any type of anti dry fire prohibitors. Now, because of the recurve crossbows simple and robust design, normally a dry fire will not result in any damage to your bow if you do happen to experience one. I think that is a remarkable feet to design a crossbow that can withstand that type of abuse. However, even if your bow can handle an accidental dry fire or two, I personally feel that from a safety stand point, that a manufacturer should include one of the above methods to keep consumers safe.

The Stock:
Another key component of a crossbow is the stock. The stock ties the barrel, trigger mechanism, and sight bridge all together. It also provides us with a safe area to hold the crossbow, away from any danger points, and provides a place for the hunter to sturdy the crossbow against their shoulder while also providing a place to rest your face or cheek so that you can see through your sight. Most stocks are made from some type of composite plastic and are produced by injection molding. We have seen some wooden stocks come and go over the years. Wooden stocks can give a bow a custom look or feel and those made from exotic woods are truly a work of art. However, because of the extra expense of exotic woods and the the process it takes to sculpt a wooden stock, it just isn’t a practical option for most manufacturers to include on crossbow models while trying to stay competitive on cost.
Most bows will either have one of two type of grips on their stocks. The most popular style of stock is referred to as a thumb hole stock. Thumb hole stocks actually have a hole located in the stock behind the grip that your thumb fits through. A traditional style stock, much like the one on your favorite rifle or shotgun, is the second most common type of stock. There is no real advantage as to one over the other. Most of the time, if you like a particular brand or model of crossbow, you are stuck with whatever type of stock they offer. Excalibur and TenPoint crossbows however, are two manufacturers that do offer some models with both types of stocks.

The Sight Bridge:
The sight bridge on a crossbow is the part of the bow that you mount your scope or sight to. It’s one of the most important features of your crossbow and yet it is one of the most overlooked when actually looking at a crossbows features. Without a rock solid sight bridge, your scope or sight would not have a solid base to mount to. Without a solid base, achieving excellent accuracy that is repeatable would be impossible. Some manufacturers incorporate the sight bridge into the trigger housing so that it becomes a one piece unit. Other manufacturers bolt the sight bridge to the stock of the crossbow. Each have their own respective advantages. However, each method is also more than capable of achieving the results us as hunters are looking for. Your crossbows sight bridge should be made out of some type of metal, not plastic. Most of the time they are machined from aluminum and will include the weaver style dovetail mount needed to mount most of todays scopes and red dots.

Arrow Retainers:
The job of the arrow retainer on your crossbow is to hold your arrow. You should be able to point your bow straight down or even flip it over, and your arrow should stay seated. Arrow retainers for crossbows can come in a variety of styles. What used to be just a piece of spring steel with a piece of shrink tubing on it, has now taken many forms in modern crossbow technology. Some bows still use the spring steel arrow retainer. However there are some other designs worth noting. The first looks and acts just like the steel retainer except that it is made from plastic. The main reason for the change in material is that the plastic one will take some of the twang out of the bow when fired. The twang sound you hear is a result of the spring steel arrow retainer vibrating like a tuning fork after the bow is shot. So by switching to plastic, it helps to eliminate that sound making the bow quieter. A few manufacturers have incorporated their arrow retainers directly into there anti dry-fire prohibitors. These arrow retainers are very ridged unlike the springy ones made from steel or plastic. When an arrow is slid underneath one of these types of arrow retainers, the arrow retainer then moves allowing for the safety to then be put into the fire position allowing the bow to be fired. Horton crossbows has just recently come out with an arrow retainer that is a floating ball bearing that comes down from the sight bridge. The ball is backed by a spring so it provides down pressure on the arrow holding it snugly in place.

Sights:
There are three primary sights that a hunter can have mounted to their crossbow. Pin and peep style sights, a red dot scope style sight, or a traditional scope style sight with magnification. Choosing the sighting system usually comes down to ones personal likes or tastes. However, some states that do allow crossbows for hunting also have stipulations on what type of sighting method you can use. Some states do not allow any kind of optics mounter to your bow. So it would be wise to check the rules and regulations of the state you live in before shelling out big bucks for the latest in crossbow scopes. So lets take a look at each sight system.
The pin and peep. In it’s simplest form it consists of an aiming point mounted somewhere at the front end of your bow. Most times mounted to the riser itself. Towards the rear of the bow, mounted to the sight bridge, there will be a a peep site. The peep site is just a piece of plastic or aluminum with a hole in it. To use this type of sight, you simply look through the hole at your aiming point, and cover up what you want to hit. Most of the time the front aiming point will be some sort of adjustable pin or series of pins, that allow you to set each one for a specific distance while also providing windage adjustment so you can move your point of impact to the left or right as needed. The pin and peep sight is sometimes found on some base model crossbow packages but higher end peep and pin sights can be found from third party manufacturers such as Bad River Outdoors. Pin and peep sights do have the advantage of not requiring any batteries like other crossbow sights, and they are impossible to fog up. However, unless a hunter has a hard time seeing through a traditional optic style sight or lives in a state where any kind of optics are prohibited, chances are you won’t be hunting with this type of sight this fall.
The Red dot sight is the next step up from the pin and peep style sight. Red dot sights normally have little or no magnification. Most red dots do require some sort of power source to operate. Usually this is a battery housed inside the sight itself which powers the multiple aiming points a red dot has. Most common red dots used for crossbows will have three aiming points but some can have just one. They also offer a brightness adjustment that allow the hunter to adjust how bright the aiming dots are. Some of the halo (holographic) type red dot sights also have an adjustment where you can change the actual reticle or shape of the aiming points. You can go from a plain dot, to hollow circle, to crosshairs, etc. With both red dots and halo sights, often times you will have a choice on what color you want your aiming points to be. The two most popular options are red and green. Red dot and halo sights are very popular for those hunters that like to have a precise adjustment compared to pins sights, or like to have a sight with an illuminated reticle, but require little to no power magnification.
A scope is the most widely used method for crossbow sights and come with the most varieties in options. Options can range from the amount of aiming points you want to the amount of magnification. There are scopes that have illuminated reticles and non illuminated reticles. Some scopes have reticles that are sighted in for crossbows of a certain speed range while other scopes allow you to dial in the exact speed your bow shoots, adjusting the reticle to fit your exact trajectory of your arrow. There are even scopes that allow you to range your target, and then dial in the exact yardage so you do not have to guess how high or how low to aim. Most manufactures include a crossbow scope of of sort when you purchase a package. And most of the supplied scopes are good enough for the beginner hunter to go out and effectively have a successful hunt. You may find that a basic scope is all you will ever need. My advice though would be hunt with what you have for a year or so before you look to upgrade. Only through real world experience will you find out if you really need something better or if there is a specific feature that you just cant live without.

The Quiver:
The quiver is responsible for holding your arrows and acting as a guard to protect your braodheads. Crossbow quivers come in a variety of shapes, sizes and configurations. They can mount under the bow or on top of the bow. Some quivers mount parallel to the bow itself while others mount parallel to the barrel. Most quivers hold three to four arrows and include some type of plastic hood to protect the blades from your broadheads from coming into contact with things they shouldn’t. Some hunters will hunt with their quivers attached to their bows while others will simply use it to transport their arrows to from their hunting location, only to remove it once situated.

That pretty much sums up all of the major components you will find on a crossbow. The examples used in this article should have given you a general idea of what each part is and how they work. Not all bows will have all the parts featured in this article. And at the rate manufacturers are developing new technologies, there may be current parts to a crossbow that are not included in this article at the time you read it. But if you were unfamiliar with the components it takes to make up a crossbow before reading this article, you now know what they are and how they each work together.


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