Despite the rise in popularity of crossbow hunting and an increase in the number of hunting crossbows available in the marketplace, a lot of confusion still exists about crossbow speeds, crossbow arrow weights, and how to choose the best crossbow arrow weight for hunting crossbows.
A reader recently submitted this GREAT question: “Every crossbow has different draw weights/FPS ratings. Should arrow weight differ depending on how powerful my crossbow is? I’ve looked and looked and can’t find a single formula or opinion on how to size the weight of the bolt to be optimal to the specific crossbow I’m using.”
This month I will unpack this question and provide some clarity on how to choose the best arrow weight for your specific hunting crossbow.
Let us begin by addressing the statement, “Every crossbow has different draw weights/FPS ratings”. This is true. But why is it true? Three main factors determine how fast a crossbow will shoot: power stroke, draw weight and arrow weight.
Power stroke is the distance, in inches, that the string accelerates an arrow down a crossbow’s flight rail. Generally speaking, crossbows that have longer power strokes will shoot faster than crossbows with shorter ones because the string accelerates the arrow for a longer distance. This is why reverse draw crossbows have an advantage over forward draw crossbows.
The draw weight of a crossbow also factors into its speed. If you have two identical crossbows with the same power stroke but the string on one is mounted at 10-pounds heavier draw weight, it will shoot faster than the one with the lighter draw weight because the force of acceleration is greater.
For example, TenPoint’s Wicked Ridge Invader 400 crossbow has a 13.5” power stroke, a draw weight of 185-pounds, and shoots a 370-grain arrow at 400 feet-per-second. TenPoint’s Wicked Ridge Rampage 360 crossbow utilizes the same stock, flight rail, and bow assembly configuration as the Invader 400, giving it the same 13.5-inch power stroke, however the string on the Rampage 360 is mounted at 175-pounds, thus yielding a speed of 360 feet-per-second with the same 370-grain arrow.
Arrow weight is the third, and perhaps most important, factor that determines crossbow speed because it is the only one of the three factors that you can directly control with your crossbow arrow choice. When a crossbow transfers the energy stored in the bow assembly to the arrow through the string and accelerates the arrow down the flight rail, it delivers the same amount of force to the arrow when it launches it each time. A light arrow is easier to move from rest than a heavy one, so your crossbow will shoot a light arrow faster than it will shoot a heavy one.
Most crossbows are marketed with an “up to” speed rating, determined by the manufacturer typically by using the lightest arrow required for the crossbow. However this light crossbow arrow may not be the best crossbow arrow for hunting.
Now that you know why your choice of arrow weight directly affects your hunting crossbow’s speed, let us discuss an arrow’s kinetic energy measurement and why you should consider its significance in the context of crossbow hunting. A lighter arrow that shoots faster out of your crossbow may be a great arrow to use for competitive target shooting, but it may not be the best crossbow arrow for hunting.
The kinetic energy of your arrow is how much energy the arrow carries in flight. In other words, kinetic energy is a measurement of how much force is exerted by the arrow onto its target. A high amount of kinetic energy means that the arrow will hit the target harder and will penetrate farther than an arrow that carries a lower amount. The amount of kinetic energy is determined by both the weight and the speed of the arrow.
Generally, a light arrow that travels faster out of your hunting crossbow will have a lower amount of kinetic energy than a heavy arrow traveling more slowly. For this reason, most crossbow hunters choose the heavy arrow and are willing to sacrifice some arrow speed because of the increased amount of penetration power that the heavy arrow will inflict upon the animal.
Next, let us address the reader’s question: “Should arrow weight differ depending on how powerful my crossbow is?” The short answer is yes. The reason this is such a GREAT question is that it helps to lay bare what I consider to be the greatest hunting advantage of shooting a high-performance crossbow. And this advantage is not what most folks might think.
Many crossbow hunters have been driven to buy a fast crossbow because they believe that shooting at the highest speed possible will yield the greatest hunting advantage. Oftentimes, they will purchase the lightest arrows for the crossbow to achieve the maximum speed. Many crossbow hunters do not take into consideration how kinetic energy yields a greater advantage than speed to the crossbow hunter with greater penetration power and an increased likelihood of inflicting a pass-through lethal blow that yields a recovered animal.
So, when you buy a more powerful crossbow for hunting, the real advantage to you is that you can shoot heavy crossbow arrows faster than you could shoot the same heavy arrows in the past. Because you can shoot these heavy arrows faster, the greatest hunting advantage of your more powerful crossbow is that it yields higher kinetic energy levels and greater penetration power from your crossbow hunting arrows.
If you purchase finished crossbow hunting arrows, my advice is to choose the heaviest arrow that you can find that fits your manufacturer’s arrow recommendations. Shooting heavy crossbow arrows have many other advantages than just increased power, like being more accurate at longer distances, making your crossbow quieter, and reducing the amount of stress to the crossbow’s parts over the long-term.
If you purchase custom built arrows or build them yourself, then you can experiment with shooting heavier arrow weights than are available in stores. You can find the equation for calculating an arrow’s kinetic energy in my article HOW TO GET THE MOST POWER OUT OF YOUR CROSSBOW. Armed with your crossbow, a chronograph, and arrows of multiple weights, you can determine which arrow weight will specifically yield both the maximum level of kinetic energy you desire along with the level of speed loss that you are willing to sacrifice for this high level of kinetic energy. And, chances are, you will have a lot of fun shooting your crossbow in the process.
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