Why Heavy Crossbow Arrows Work Best

Your teacher always told you there would be a real-world application for what you learned in math class — that now includes hunting with a crossbow.

Why Heavy Crossbow Arrows Work Best

The author has learned that shooting a heavy arrow provides outstanding penetration and quiet crossbow performance.

The Florida sun was sinking fast in the western sky when a big boar hog fed to the edge of the palmettos. He was preoccupied with filling his stomach, allowing us to circle downwind and plan a route to stalk close. Taking one step at a time, we closed the distance, often stopping to check on the hog’s location with my binocular. A dense wall of palmettos provided the perfect cover, and before I knew it, I could hear the oinker crunching his dinner.

My heart was racing, but I stayed calm and waited for the right opportunity. Catching glimpses of the hog through the vegetation, I hoped he would turn broadside. I had a hole in the green palms about the size of a softball to shoot through and would need to thread the needle.

The hog was only 10 yards away when he finally turned, giving me a shot at his vitals. I had to take a step to my right to line the boar up with my shooting lane before leveling my crosshair on his chest. When I squeezed the trigger, my arrow zipped through the big boar like a hot knife through butter.

To my astonishment, the hog barely reacted because he did not hear my TenPoint Nitro XRT crossbow. The hog walked to his left, looked at us as he was wandering by and then laid down 30 yards from where he was shot.

Speed is a big part of marketing crossbows, but hunters should consider cashing in some horsepower for penetration and silence. Part of the speed equation is shooting lightweight carbon arrows. These carbon projectiles are durable, but the less weight in your arrow setup, the more noise your bow will produce. Let’s examine a few specifics.

Arrow Weight

With several archery aficionados in camp, we did a little experimenting and made some heavier than normal arrows. Everything adds up when it comes to putting an arrow together, from the nock to the broadhead, allowing a hunter to customize a projectile for a deadly combination of speed and stealth.

The Nitro XRT is speed rated at 470 fps. The chronograph reading is consistent with the TenPoint Pro Lite 20-inch carbon arrow weighing 370 grains with a lighted nock and field point. TenPoint’s Evo-X Lighted CenterPunch Premium Carbon Crossbow Arrows weighs 451-grains, including 100-grain field tip, and still flies close to 400 fps.

Add It Up

Working with Easton Archery, we added weight to an arrow by looking at all the components. Aluminum inserts weighing 40 grains were replaced with brass inserts weighing 100 grains. We used an Easton Carbon Bloodline, weighing 10.5 grains per inch, and inserted a small-diameter carbon arrow inside. With an Alpha nock, NAP QuickSpin fletching and a heavy 150-grain broadhead, the final arrow weighed just shy of 700 grains.

Do the Math

The heavy arrow was incredibly stable out of the Nitro XRT. The point of impact on a 30-yard target was just 2 inches lower than with the CenterPunch weighing 451 grains. A minor adjustment on the scope brought the point of impact to the bull’s-eye. 

Why Shoot a Heavy Arrow?

The weight of a projectile is directly correlated to penetration. Take a wooden spear and throw it into a target and see how it compares to a steel spear. Yes, that’s a drastic comparison but provides a visual to what weight does for penetration. It all comes down to kinetic energy.

Speed vs. Weight

Let’s take a quick look at how speed, arrow weight and bow design can change kinetic energy and ultimately, the effective range of different crossbows. If we look at some of the popular crossbow models available today and match them with arrows based on the manufacturer’s recommendations for draw length and draw weight, we can quickly see the kinetic energy produced. I like to use a chronograph to measure the speed that a specific bow would shoot an arrow to calculate the exact kinetic energy for any combination of bow, arrow, and broadhead.

Equation

Kinetic energy is the energy an object has owing to its motion. Kinetic energy in foot-pounds (fpe) is equal to arrow weight multiplied by the velocity squared, then divided by 450,240. For example, if an arrow with a mass of 370 grains is moving at a velocity of 430 fps, the kinetic energy is 152 fpe.

Our heavyweight 682-grain arrow was shot at 380 fps, producing 219 fpe. The energy factor was exceptional, and the arrow was still flying at speeds most crossbows don’t achieve.

Understanding Decibels

The decibel scale is logarithmic and works in a different way to the scale on a ruler, which is a linear scale. On a ruler, a distance of 12 inches is twice as long as a distance of 6 inches and 18 inches is three times as long. The logarithmic decibel scale has a greater factor of measure, as it goes up in powers of 10, which means every increase of 10 dB on the scale is equivalent to a 10-fold increase in sound intensity. In layman’s terms, the increase in sound nearly doubles in loudness. That means a sound of 20 dB is 10 times more intense than a sound of 10 dB.

Now that you understand how to measure the pressure of noise, you can look at what a heavy arrow does to quiet a crossbow. Using a smartphone app to measure decibels, we held the phone 6 inches from the crossbow when fired.

The Nitro XRT shooting the 451-grain arrow produced a decibel reading of 95.1 dB, where the 682-grain arrow produced 91.1 dB. Knowing how the logarithmic decibel scale works, we see the lighter arrow is almost five times louder coming off the rail. That is a significant difference in noise harnessed by the arrow simply by adding weight.

Fine-tuning arrow weight and arrow speed will provide optimal kinetic energy and decibel readings to get the job done.
Fine-tuning arrow weight and arrow speed will provide optimal kinetic energy and decibel readings to get the job done.

Field Test

In the case of the hog, the penetration was quick and efficient. The decibel reading of the bow was so quiet that the hog didn’t even hear the shot. The tradeoff between speed and performance was well worth it.

During the day, we had a lot of time to set up targets and see how the bows and different weights of arrows performed. The decibel readings were most interesting.     

What Does It All Mean?

Anyone who has hunted whitetails knows how jumpy the animals can be with the sound of a bow releasing an arrow. Any advantage you can gain by quieting your bow reduces the chances of a deer jumping the string. The other consideration is penetration on a less than ideal shot. If you do catch bone with your broadhead, it has a much better chance of penetrating with extra weight to maintain energy. Finally, a real-world math problem worth solving!

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