By: Stephen Hafvenstein

The Background

Speed, everything these days has to be fast, fast bows need to shoot fast lightweight arrows, or so we are told. But, does this really matter? Is it better to shoot a blazing fast arrow that will reach the target faster, or a heavier arrow that will reach the target slower? We decided to run some tests to weigh out some factors that play a role in this debate. Here is what we did.

The Test Setup

For this test, we used a Mathews NoCam HTR bow set at IBO specifications (draw weight at 70 pounds with a draw length of 30 inches). The IBO rating on this bow is 330 feet per second (fps). For the arrows, we used Black Eagle Spartan’s cut at 29 inches with a spine  of 300 and a weight of 9 grains per inch (gpi).

To change the weight of the arrow we used field points with a weight of 100, 125, 150, 175 and 200 grains, all points had the same tip design. Our insert weight was 28 grains, the bushing weight was 10 grains, the nock was 9 grains, and the vanes (3 total at 6 grains) weighed a total of 18 grains. Once the arrow was set up, we weighed the entire arrow on a digital scale to come up with total arrow weights (all components installed, lightest to heaviest) of 429.45, 454.67, 479.23, 504.82 and 529.51 grains. In addition to our test arrows, we also ran numbers from an IBO arrow with a weight of 350 grains. Our Front of Center (FOC) for each arrow (lightest to heaviest) was 10.77%, 12.82%, 14.65%, 16.31% and 17.80%. We shot each arrow three times into targets set at 10, 20, 30 and 40 yards and averaged the time the arrow took to get to the target. We used sound to determine the time it took the arrow to clear the string to the time it took the head to hit the target. By recording the shot with a Deity V-Mic D3 Pro, we were able to calculate time down to the millisecond by averaging the audio wavelengths of the shots. Finally, we purchased two archery calculation programs to compare our numbers against. We entered our specifications into the programs and ran them to calculate the results. After completing our tests, we compared our results against the two programs and found that all three sets of data were within one percent of each other. For our research we used the data from our tests due to the fact this takes into account the environmental and human aspects of shooting a bow that we felt would represent a better picture of real-world conditions.

Other Variables

We took this test a few steps further by calculating other variables that affect the flight of an arrow as well as the reaction times of game species.

DRAG:

The first calculation we ran was arrow drag. Due to air density, gravity, wind, humidity, arrow flight performance and arrow components (fletching, arrow wrap, arrow finish…etc.), an arrow will experience speed loss during flight. We calculated this via speed loss formulas for each variable and subtracted the differences in time it took the arrow to hit the target at each distance. For example, our 529.51 grain arrow exited the bow at 270.94fps, with no drag; our arrow would reach the 10 yards target in 0.1107 seconds. However, it took the arrow 0.1120 seconds to reach the 10-yard target, a difference of 0.0013 seconds. Although this number is extremely small, it represents the drag an arrow experiences during flight due to a number of speed loss variables. As a rule of thumb, as distance increases, arrow speed will decrease as it experiences a longer duration of drag. In an ideal world with no speed loss, the 529.51 grain arrow would fly a constant 270.94fps throughout its entire flight path.

SPEED OF SOUND:

The second variable we accounted for was the speed of sound. If a game animal does not see you take the shot, the only way it will know a shot was taken, is to hear it. The speed of sound is 1125.33fps. At 10 yards the sound of the shot will reach the game animal in 0.027 seconds, once again, this is an extremely small number but it represents a time variable. We took this into account when determining the time, a game animal has to react to a shot and calculated this for each distance we shot. Additionally, we marked out where I would plant my feet each time I shot to remain consistent. We then calculated the distance from where the arrows left the bow string to the microphone and the distance of each target to the microphone to account for the time it takes the sound to reach the microphone, yet another variable. Once again, as distance increases, so does the time it takes for the sound to reach the animal.

 REACTION TIME:

The last variable we calculated was the reaction time of an animal. There were quite a few variables in the reaction time, some of them cannot be calculated such as the individual response of an animal, but we calculated the variables that can. For reaction time, we took into account the time in milliseconds it takes for an animal to register noise and for the neurons to carry that to the brain. After studying many scientific articles, we felt confident that by using the audible reaction time of a rat, it would easily account for that of a game animal. Rats have one of the fastest reaction times in the animal kingdom, much faster than that of whitetail deer for example. The rat had an audio reaction time of 10 milliseconds, 0.01 seconds. We also took into account the time it takes the neurons to carry the signal from the brain back to the muscles and for the muscles to contract. For this we took the reaction time of a mid-sized dog, the reaction time was 40 milliseconds, 0.04 seconds. This is in a perfect world, it does not take into account the “surprise” factor, individual response of an animal (time it takes to recognize the sound of a bow shot as danger), or the time and speed it takes to “jump” or “duck” the arrow. We chose to use the data from a rat and a dog due to their smaller size and faster reaction times than most game animals. A rule of thumb, due to the distance of the animal’s audio receptors to its brain, the smaller the animal, the shorter distance the neurons have to carry the signal to the brain and back to the muscles, therefore smaller animals generally have faster reaction times than larger animals

Our Findings 

KINETIC ENERGY:

Kinetic Energy (KE) is the amount of energy an arrow possesses and transfers to its target. The lethality of an arrow has very little to do with the KE it possesses, however, KE is a very important variable for the lethality of a bullet. Watching a bullet hit ballistic gel at a super slow motion, gives the viewer an excellent understanding of the shockwaves a bullet sends through the gel, those waves are the KE that the gel is absorbing from the bullet. Bullets travel at such a velocity that the energy it transfers to the gel or animal is enough to send a lethal amount of energy into the tissues surrounding the path of the bullet. Arrows do not carry enough energy to do this, its lethality comes from broadhead design and durability, arrow design and durability, and the penetrating power (momentum) it carries. According to the charts we could find online on kinetic energy required to harvest big game animals, all our arrows had more than enough kinetic energy, even double in some cases to harvest big game. Even our IBO arrow had more than enough kinetic energy to harvest any North American big game species as well as Cape Buffalo. This made us question how useful kinetic energy really is for the archer. We ran some further tests on KE using the ballistics of a 42 grain, .22 round with an exit velocity of 1220 fps. The kinetic energy result we got back from our calculations was 138.78 ft. lbs. (see table 1), this according to the KE required to harvest big game charts, was double the amount of KE required to harvest a Grizzly, Moose or Cape Buffalo. However, the momentum for the round was grossly inadequate (0.229 pound seconds) for harvesting any large game species. Therefore, KE is a direct component of velocity and the “shock” factor of the projectile hitting the target. We also put our bow numbers in a popular online archery calculator with a 200 grain arrow and the kinetic energy the program calculated was 61.4 ft. lbs. Which, according to the online calculator, was enough to harvest large North American game species such as elk. An arrow and bullet are two completely different projectiles, however, by running our tests and comparing the KE of both projectiles, we were able to determine that for KE to be lethal you need high velocities that are unattainable by an arrow.

Additionally, the minute amount of KE the arrow possesses is quickly lost upon impact. Elasticity of the animals hide, and the density and thickness of hair, hide and bone absorb the KE as its non-directional energy is displaced in all directions. Momentum on the other hand is a directional energy, which is key to driving the arrow through the animal. 

We made some additional calculations and discovered that a heavier arrow retains more of its KE the further the shot versus a lighter arrow. The difference between the lightest arrow and the heaviest arrow was 2.122 ft. lbs. at 0 yards, 2.244 at 10 yards, 2.317 at 20 yards, 3.014 at 30 yards and 3.260 at 40 yards. As you can see from table 1, the heavier arrow retained more energy as distance increased compared to a lighter arrow. However, as arrow weight increases, it will reach a threshold where the KE of a lighter arrow will be greater due to the velocity of the shot.

MOMENTUM:

Momentum is a measurement of the force an arrow carries into the target (measured in pound seconds). As a rule of thumb, the greater the mass or weight of an arrow, the more momentum it carries into the target. Similar to kinetic energy, as the arrow flight increases in distance, the pound seconds between the lighter and heavier arrows increases, or, the heavier arrow is more efficient at retaining its momentum (see table 2). As momentum increases, the force required to stop the arrow increases. Therefore, an arrow carrying greater momentum will penetrate further into its target. As a hunter, our goal is to get clean passthrough shots that cause as much damage as possible, momentum is key for this. Having an arrow carrying a greater degree of momentum also helps arrow penetration for the times an arrow finds a bone or cartilage. The thickness and density of hair, hide, bone and flesh will play a role in how quickly the arrow will lose momentum. That being said, game animals with thicker or denser hair, hide, bone and flesh, will require a heavier arrow with more momentum than a game species that exhibits thinner and less dense characteristics. This is an entirely different test that we will run and thus will discuss this further once we have completed additional tests.

ARROW ARC:

We compared the fastest arrow (429.45gr) to the slowest arrow (529.51) to see the change in rise along the flight path. The difference between the two arrows was 1.22” at 10 yards, 1.61” at 20 yards, 1.21” at 30 yards and they both zeroed out at the 40-yard target. These numbers are small and likely not be of great concern during a hunt, but, as we all know, hunting has so many variables and even a hundredth of an inch can make a major difference. Is this a major factor in choosing your arrows? We say not at all; the benefits of shooting a heavier arrow far outweigh the arc of the arrow. 

ARROW SPEED:

The exit speed difference between the heaviest arrow and the lightest arrow was 26.19fps (table 3). The time difference between the two arrows at 10 yards was 0.0.010 seconds, at 20 yards it was 0.020, at 30 yards 0.028 and at 40 yards 0.037 (see table 5). The average blink of an eye is between 0.1 and 0.4 seconds, the time difference between the slowest and fastest arrow is faster than the blink of an eye and therefore does not play even a minor role in choosing an arrow.

TIME A GAME ANIMAL HAS TO DODGE THE SHOT:

By subtracting the speed of sound and reaction time variables from the time it takes the arrow to reach the target, we can determine the amount of the time animal has to dodge the shot. For these calculations, we will use our heaviest arrow. At 10 yards, the arrow reaches the animal in 0.112 seconds. By subtracting the animal’s audio to brain reaction time (0.01 seconds) and the brain to muscle reaction time (0.04 seconds), speed of sound (0.0266) and the distance the sound travels to the microphone, we come up with a time of 0.035 seconds (see table 6), a time nearly impossible for the animal to dodge the arrow. As distance increases, the time an animal has to react also increases. For example, the same arrow will reach the 40-yard target in 0.460 seconds. The audio of the shot (speed of sound) will reach the animal at that distance in 0.1066 seconds, the audio to brain and brain to muscle stimulation will remain constant, at 0.01 and 0.04 seconds and the sound to microphone times will increase. By subtracting these numbers, we get a total time of 0.303 seconds that the animal has to react to the shot. Which is the same amount of time it takes one to blink, as hunters we have seen an animal dodge an arrow at these ranges, however, in most cases the animal is already aware of the hunter and is ready for flight, by adding the surprise factor, it makes it nearly impossible to dodge the arrow.

 What Matters More Than Speed

BROADHEAD SELECTION:

Broadhead selection should be made based on these factors: durability, edge bevel (single recommended), edge sharpness, tip design (cut on contact recommended) and blade length and steepness (a gradual rise and longer length recommended). We like to use fixed blade heads but will use mechanicals in certain situations. Just remember that with a mechanical broadhead you will have a greater cutting diameter and steeper blades in most cases. This will slow down your arrow by adding greater resistance upon penetration. Therefore, you should use a heavier arrow with more momentum to drive the arrow further into the target. As a hunter, our goal is to harvest a game animal while ensuring a clean quick kill.

FRONT OF CENTER (FOC):

FOC is the percentage of arrow weight situated forward of center point. Having a well-balanced arrow that flies well is extremely important. An arrow with a FOC that is too low or high will experience erratic flight, and if the FOC is too low, arrow penetration will substantially decrease. Having a FOC somewhere between 12-18% is a good place to start for excellent arrow flight and penetration and is what we recommend.

SHOT SELECTION:

Choosing your shot plays a major role in hunting success. For instance, taking a shot at a game animal that has sensed your presence, has you in their peripheral, or has spotted or winded you, completely removes the surprise factor, due to the fact that the animal has already determined that danger is near and it is prepared for flight. If the animal has spotted you the speed of sound factor is removed from the equation, movement gets to the animal instantly, sound does not. In addition, take good shots, I see video of hunters taking Robin Hood style shots or shots of deer angled in such a way that the shot will most likely result in a wounded animal. Choose your shots wisely.

ARROW SELECTION:

A light arrow will not carry the same momentum as a heavier arrow; therefore, a responsible hunter should strive to select an arrow that will have enough momentum to travel through the game animal. Of course, there are so many variables to hunting you cannot always guarantee a clean passthrough, arrows hit bone or cartilage, stuff happens, but a heavier arrow will give you better penetration which is key to harvesting an animal. Arrow shaft diameter also plays a major role in its ability to penetrate the target, having a shaft that is at least 5% smaller that the broadhead diameter at its widest point ensures better penetration by reducing friction as it passes through the wound channel created by the broadhead. That being said, you do not want to get a shaft that is too small, as that can have an effect on arrow durability. It is also important to choose an arrow that has a tapered shaft, most arrow manufacturers make a majority of their arrows with tapered shafts. Arrow manufacturers offer arrows at variable grains per inch (gpi), purchasing a heavier shaft will get you extra arrow mass, just remember to keep your FOC somewhere between 12-18%.

BOW SELECTION:

We mentor a lot of young hunters trying to get them involved in the outdoors, one thing we tell them when purchasing a bow, is to get one that fits them and that they can shoot well. Having a bow that you shoot well and can consistently achieve good arrow groupings, is more important than having a speed bow. We ran some tests on bow speed, and just like arrows, having a bow that shoots 60 feet per second faster than our slowest bow, makes very little difference in the time an arrow reaches the target. Furthermore, if you cannot shoot a bow accurately and with confidence, how are you going to shoot when the opportunity to harvest an animal comes along. Bow cycle, and how quiet and smooth it shoots, is also very important. aster bows tend to jump a little more due to the violent nature required to get the extra speed out of the bow. When considering the surprise factor, a quiet bow with lower decibel levels, gives you a greater edge. 

SCENT AND CONCEALMENT:

We have talked about losing the surprise factor, scent and concealment play a huge role in this. If you do not control your scent and play the wind correctly you run the risk of an animal winding or spotting you. Keep this in mind when out in the field, check the wind and make sure you are well concealed. One thing I hardly ever see hunters carrying around these days is a small bottle of wind checker. I have a bottle of talcum powder that I give a puff every once in a while, to see what the wind and thermals are doing. Do not rely on scent eliminating clothing and electronic devices, they play a role, but be sure to check the wind and its effects on scent control.

BOW TUNING:

This is a major factor in the penetrating ability of an arrow. Having an arrow that flies poorly along its flight path, will experience greater drag  and thus will lose momentum and the ability to penetrate further into its target. A properly tuned bow with arrows that fly well is crucial for hunting success. If you shoot fixed blade broadheads, tune your bow to them before you go out on a hunt. I have seen hunters punching out the bullseye with a field point, only to have their broadheads hit all over the target when practicing before the hunt. Make sure to check your arrow flight with a broadhead, there can be a difference of a few inches between the two, a properly tuned bow and a good broadhead will shoot similar groups as a field point.

PRACTICE:

Shooting your bow in a number of positions and distances before season begins, is a great way to punch your tag. When hunting you rarely, if ever get the perfect shot. Game animals appear from places and distances we least expect, rarely is your shot the same as is it practicing in your front yard. Practice shooting from your stand, behind you, sitting down, standing up, on either side of the tree, in every position you can think of always remembering to wear your safety harness, go through possible scenarios in your mind and try replicating them as close as you can. Practice from the ground, standing, sitting and kneeling. By going through the motions before season, it will make you a more confident hunter and prepare you for when you take the shot.

Conclusion

I hope that this test has been an eye opener for many of you and that it helps make you a better hunter. Does arrow speed really matter? We say very little compared to other hunting variables. Next time you decide on selecting a new arrow setup, we hope you take our tests into consideration. Traditional archers pay very close attention to their arrow weight and hunting setup, their bow it is an extension of their body. They shoot heavy arrows well over 500gpi at speeds well under 200fps and they have been harvesting game since the invention of the bow and arrow. Good luck on your next hunt, enjoy every moment you have in the good Lord’s outdoors and blessings on your next outdoor adventure.