More Arrow Weight Matters On Modern Bows
A technical look at shooting heavier arrows.
Tim Knight | September 10, 2016
More weight on your arrows is a good thing. Believe me? If you don’t believe me, take a look at some testing done by Kris Wall that’s included here. First, let me give you an example.
It was the first week of November last season. I was watching the weather report, and I was also paying attention to the river reading and level of the Oconee River. My plans were to hunt a bluff on the Oconee between an oxbow lake and a big slough. To get to this spot, I would have to wade across the slough.
After a 45-minute truck ride, and then a 15-minute ride on the 4-wheeler, I finally placed my Lone Wolf climber on my back with my waders attached and began a 10-minute walk to the slough. At the slough, I slipped on my waders and crossed the water. Then I removed my waders and climbed the slick bank to the top of the bluff.
This bluff was 40 yards wide and ran in a semi-circle around the back side of the oxbow lake. It ran a distance of several hundred yards and joined two huge cane thickets at each end. This bluff is the only travel route out of the water when the river is high.
It makes a natural funnel that pinches down like the middle of an hour glass, and I was in that pinch spot.
The wind was out of the east, which was perfect, and it meant that I needed to climb a tree as soon as I got to the top of the bluff. I found this spot while stalking hogs earlier in the year. A great advantage to stalking hogs in the off season is that you find bottlenecks, funnels and saddles, not to mention remembering food source trees that you walk by while hunting. Log these food trees and food sources in your memory or in a log book to return to and check for sign and to see if they are bearing mast in the fall.
Every serious bowhunter should learn all of the food sources in their hunting areas, and we should know how to recognize the trees by their bark and leaf patterns.
I slipped up a sweetgum tree in my climber, quiet as a church mouse. It was 3 p.m. when I got settled in my tree. I took out my bottle of Voo-Doo deer lure and poured some in the cap and broadcast it from the tree in several directions. I do not like to walk around my stand and put out lure because I feel this can compromise the perimeter of your stand area.
At 3:35, I heard a loud splash about 100 yards away and heard something crashing through the thick cane.
And it was headed my way.
I grabbed my bow and stood up just in time to see a big doe and two yearlings run by. Less than a minute later I heard another splash… followed by a loud grunt. I looked down the buff and caught a glimpse of antler. I came to full draw as the buck came into view at less than 20 yards. The buck locked up on the very spot I had thrown out the lure and was lifting his head and doing a lip curl. He was about 15 yards and was quartered to me as he swung his head left and right. I got my one-pin sight settled on the front of his shoulder—due to the fact he was quartered toward me—and squeezed the trigger.
You may ask yourself, why take a quartered-to shot?
If you know your equipment and its ability, and you know how much kinetic energy, momentum and FOC measurement (front of center) your setup has, you can take this type of shot.
I asked Kris Wall to contribute to this article by doing some testing with different weight setups, and his findings and opinions are listed below.
Kris has 29 years of bowhunting experience, and he’s a full-time bowhunter. So far he has taken more than 80 deer taken with bow. He’s also an elite bow tuner and elite tournament archer, with a second-place in an ASA State Championship and multiple 3D wins. Kris is also the archery moderator on the GON Forum (forum.gon.com).
Kris Wall’s Test
The following is a report written by Kris about his tests, shooting different weight arrows at typical hunting distances. His test notes are at the end of this article.
I took three different weight points most commonly used by bowhunters. The most popular point I shot was the 100-grain, followed by 125-grain, and lastly a 165-grain point. I shot multiple groups to confirm accuracy and trajectory from the three different weights. I first shot the three different weight arrows at 20 yards, which is probably the average shot distance on a whitetail deer in Georgia. I then went back to 30 yards to see how much trajectory variance would occur. The results were similar, although the gap did widen some.
I would still say the variation in drop would be fine for bowhunters aiming at the vitals of a whitetail.
The main focus of the test was to show there is not a significant drop in arrow trajectory at average bowhunting distances. The benefits from shooting heavier arrows outweighs the extra little speed you gain. The test proved that, I believe.
The pictures above represent the most common results that I experienced in testing while shooting multiple groups.
Kenetic Engery (KE) and Momentum (MO) are often interchanged, and they have similar meanings because they both use speed (velocity in the case of momentum) and mass in their equations. I think of KE as the energy required by a broadhead to cut tissue, hide and bones. I think of MO as the force required to stop that arrow from cutting tissue, hide and bones. While both are important in bowhunting, in my opinion, momentum is more important, especially on marginal shots where bone is encountered. You simply want that arrow to penetrate as far as it can. We know that a light arrow also sheds KE faster than a heavy arrow. So while a bow may show you similar KE results from different weight arrows, we know that downrange they are not the same. Unlike KE calculations, the heavier you go on an arrow, the momentum continues to increase. This can only help shots downrange, as well.
We also know that a heavier arrow is quieter than a lighter arrow. This is because more of the bow’s energy (sound in this case) is being transferred into the arrow. In case of a lighter arrow, the sound is wasted energy, making the bow less efficient. Another benefit of a heavier shaft is less resistance to wind drift.
If surface areas are equal on two shafts, a heavier shaft will plane less due to crosswinds. This is a well-known fact in field archery, and western hunters have to deal with this problem more than us east coast hunters. Think of hitting a ping-pong ball compared to a golf ball in a crosswind. Both have similar surface areas, but the golf ball is able to cut through the wind much, much easier.
More thoughts… with today’s rangefinders, it’s not nearly as important to have less drop as years past, especially when the deviation is only 1 to 2 inches. Today’s bows are efficient enough to make that not nearly as important. Convert sound and vibration (wasted energy) into potential energy by way of the arrow.
Find Your FOC
FOC (see formula in chart below) is the balance point measured from the very front of the arrow. It’s important when measuring FOC to measure with the broadhead installed.
Let’s look at an example. You have an overall length of 30 inches. Half of that would be 15 inches, which is the very center of the arrow. The balance point of the arrow is 12 inches from the front—15-12=3 inches front of center. Three divided by 30 is .10. Multiply times 100 to convert to percent. This arrow would yield a 10 percent FOC, a very respectable number.
I think a good range is in the 8 to 15 percent range, with my personal setup at 14 percent. We know that an arrow needs weight in the front to stabilize out of the bow. Try throwing an arrow in the backyard with no point weight, and you’ll quickly see how erratic it will fly.
Overall Arrow Weights
I think a good average hunting arrow should fall in the 6 to 8 grains per pound of bow weight, with lighter bows maybe even closer to 9 to 10 grains per pound. A typical 60-lb. bow should be in the 360- to 480-grain range, a 70-lb. bow in the 420- to 560-grain range.
As game weight increases, lean toward the heavier end to keep momentum as high as possible. Remember, KE will stay the same, but momentum will increase with the heavier weights.
I think that some youth and female shooters try and get a certain FPS out of their bows because they shoot lower poundage, while they should be focusing more on their actual arrow weight. As I always say… go heavy, or go home!
Tim Knight Wraps It Up: Weight Matters
As the Redhead X-1 pro Blackout arrow tipped with a 165-grain, all-steel Bipolar broadhead drove through the front of the shoulder of the swamp buck, he mule kicked, stumbled and then did his best to run past me into the thick cane. This was followed by a loud crash a short distance away.
My personal setup now is a PSE Carbon Air set on 58 pounds at 29 inches with a 438-grain total weight arrow, which includes a 165-grain, all-steel Bipolar head and an Ignitor lighted nock in the rear.
This setup shoots 281 FPS and creates 76.6 foot-pounds of kinetic energy with awesome momentum.
Google “backcountry bowhunting,” and use the formulas on their website to figure your setup’s KE, Momentum and FOC.
After a short wait, I climbed down and followed a heavy blood trail a short distance to the big 9-point swamp buck. The old warrior was lying there with my broken arrow shaft by his side.
This buck was later aged by a biologist at 6 1/2 years old. He now hangs on my wall, and the memory of this hunt is forever embedded in my mind.
Seems like I learn something with every hunt. What I have learned in archery is that heavier is better. Think of why a log truck or freight train is so deadly even at slow speeds. It is because of the stored energy in their weight and momentum. Remember Kris’s analogy of throwing a golf ball verses a ping-pong ball. Both have similar size, yet one is much heavier and will do much more damage at impact.
Next time you think lighter is better, you might want to “just weight a minute.”
Kris Wall’s Test Notes
KE = (arrow weight x speed (squared) / 450240 measured in foot/pounds.
MO = (arrow weight x speed) / 225400 measured in slugs.
FOC = (1/2 overall arrow length including point-balance point) / overall length x 100 measured in percent.
Test arrow weights, speed And measured variables
Bow used: 68-pound, 28.5 draw length.
100-grain point: finished weight 400 grain; 300fps; 79.95 ft/lbs KE; .532 slugs MO; FOC 9.15 percent.
125-grain point: finished weight 426 grain; 291fps; 80.12 ft/lbs KE; .550 slugs MO; FOC 11.42 percent.
165-grain point: finished weight 468 grain; 278fps; 80.33 ft/lbs KE; .577 slugs MO; FOC 14.48 percent.
• Measured drop variation of the three arrows at 20 yards was 1.25 inches.
• Measured drop variation of the three arrows at 30 yards was 2.2 inches
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