In last month’s article, I emphasized the flight advantages that are created when an arrow has extra weight in the tip or front of the shaft. This is referred to as Front of Center or FOC. If you are looking for a more thorough review on that subject, a quick Google search will turn up tons of information, including illustrations and formulas on how to calculate this important variable in creating a lethal arrow. In this article, I am going to focus on additional things to consider when selecting your hunting arrow.
SPEED AND TRAJECTORY
It is no surprise that adding point weight to increase your arrow’s FOC also adds overall weight to the shaft and decreases the arrow’s speed. As arrow speed decreases, pin gaps or sight tapes will expand, making yardage estimation increasingly important as the arrow slows down. If I was always going to take shots inside of 30 yards at precisely known yardages, I would probably shoot a 600 grain arrow with a 200 grain broadhead. In Africa, many of the hides provide these types of shot opportunities. Additionally, many tree stand or ground blind hunts in North America provide similar controlled environments. If you are going to bowhunt exclusively on these types of hunts, I’d highly recommend selecting a heavy shaft that is complemented with a heavy insert and broadhead. Your bow will be quieter, your arrows will be more durable, and your arrows will be packing more momentum when they meet their intended target.
However, most bowhunters find themselves hunting multiple species in diverse environments every season. Unless you have the luxury of having dedicated bow and arrow setups for the different environments and species you will hunt, I’d suggest settling on a hunting arrow that provides a good balance of FOC, total arrow weight, and speed. For me, I like an arrow that weighs at least 400 grains but is not heavier than 440 grains. I’d argue that the majority of archers who are shooting a modern compound bow could find an arrow in this range that would make them happy as well. This, of course, assumes that we are talking about draw lengths, bow poundages, and bow models that are within the norm for today’s modern archer.
An arrow in this weight range will still carry enough energy downrange to provide excellent penetration and its trajectory will be somewhat forgiving when you are off a yard or two in a reallife hunting scenario. With that being said, there is a huge misconception that bows shoot flatter than they really do. No matter how fast you are shooting, I highly encourage every archer to engage in practical testing on their home range to get a feel for just how critical yardage estimation is in the field. The best way to do this is to put a bullseye on your target that is the size and shape of the vitals of the animal you are hunting. Aim at the middle of these vitals from various yardages while using the wrong pin or wrong setting on your sight tape. This exercise will show you that any shots over 30 yards become increasingly unforgiving when it comes to knowing the yardage to your target. Understanding just how critical it is on foam will help ensure you don’t rush a shot in the field on fur when you are tempted to cut a corner and not use your rangefinder properly.
To drive this point home, I’ve included images that illustrate my own testing results. All of the arrows in the included images were shot while aiming with my 50 yard pin at ranges from 40 yards to 60 yards. One image shows how my impact point changes while being off +/- 5 yards, and the other two images illustrate the painful reality of being off by +/- 10 yards. As illustrated, my arrows impact 12 inches low at 60 yards when I aim with my 50 yard pin. For the record, I shot a 410 grain arrow at 292 feet per second in these tests. I also shot at least five arrows from each yardage to establish an average location for the photos.
ENERGY
If you’ve paid attention to the chatter inside an archery shop, you’ve probably heard the terms “kinetic energy” and “momentum” thrown around during arrow conversations. These are the two terms that are used most often in archery to describe the lethal power that an arrow possesses once it is in flight. Kinetic energy is the more commonly used measurement, and it is calculated using the arrow’s speed in feet per second, the arrow’s weight in grains, and a mathematical constant.
Kinetic energy was a hot topic in the early days of archery because bows were not able to store and transfer as much energy as today’s bows can. As a result, a lot of time and research were invested into establishing ethical thresholds of kinetic energy for big game harvest. Ironically, all of those thresholds are now easily surpassed with today’s equipment, and in many cases, even youth bows are capable of producing kinetic energy on par with the adult bows of yesteryear. In light of that, there is a growing movement inside the archery world to focus on momentum instead.
Momentum is a much easier equation to remember because it is simply calculated by multiplying the mass (weight) of the arrow by the velocity (speed). It is not an actual measurement of energy, but it does provide an indication of how a moving object will react to forces that try to stop it. Physicists refer to this as the moving object’s persistence, which is why the letter p is used in the momentum formula.
In the case of an arrow, resistant forces like wind, gravity, hide, bone, flesh, and organs will be the ultimate test of its persistence. The best way to think about momentum is to imagine what it takes to stop a freight train with 100 cars traveling at 5 miles per hour versus a passenger car that is traveling 60 miles per hour. Intuitively, we know that if the car and the train were to collide headon, the car would immediately stop and the train’s momentum would carry on for a brief period of time. In short, the train’s mass was way more important than the car’s velocity in the momentum equation. The same can be true for your hunting arrows.
A few minutes online will turn up hours of great reading on both topics and it will also reveal that experts aren’t widely in agreement on which measurement to rely on when it comes time to select your arrow. I lean toward momentum being a better predictor of arrow penetration, but I often find that momentum fanatics sacrifice speed and trajectory on the altar of bowhunting practicality. I have spent considerable time shooting arrows through chronographs from 0 to 50 yards, running calculations on spreadsheets, and doing unofficial research on my hunts. When I consider all factors, I continue to settle on arrows that weigh between 400 and 440 grains for an excellent combination of kinetic energy, momentum, and trajectory.
DURABILITY
Arrow toughness is almost impossible to measure objectively because arrow spine, components, and construction materials all drastically impact how an arrow will behave when it strikes a hard object like bone. It is even more complicated when the arrow is subjected to a shearing force like the shoulder moving backward into it when it is lodged inside of the chest cavity of an animal. Having said that, it should be no surprise that the toughest arrows are usually the heaviest arrows. Easton’s Full Metal Jackets (FMJs) and the new for 2018 Xtorsion from Victory are arguably two of the toughest families of arrows that money can buy. In both cases, they are very heavy and will usually result in a finished arrow that weighs in excess of 500 grains if you add weight in the front of the shaft to get optimal FOC. The FMJs feature a high-strength carbon core that is wrapped in a 7075 aluminum jacket, and the Xtorsions feature layers of high modulus carbon fiber and 304 stainless steel.
All arrows tend to get nuked on impact when they are shot into a rock pile or when a bull elk snaps one off on a tree when he’s leaving the scene of an accident. In light of that, durability isn’t a major factor for me personally in arrow selection. However, as I mentioned before, if I were hunting in controlled environments with known shot distances, I’d shoot the toughest, heaviest arrow I could find. In the meantime, the majority of arrows on the market that feature the spine I need to shoot are all very similar in overall durability.
In my experience, the most important thing you take into the field as an archer is confidence. Each fall, I strive to be confident in four things – my shooting ability, my mental preparation, my conditioning and fitness, and my equipment. I’m guessing that, once again, a demanding work schedule and the deliciousness of tacos will put one of those goals in jeopardy and I’ll get to rely on the extra layer around my midsection as an emergency calorie stash. However, one thing I’ll know for sure is that my arrow and broadhead combination will do its job when I manage to do mine.
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