Published by kbrando on 20 Aug 2008 at 12:02 pm
Top Hunting Arrow
When it comes to real bowhunting, don’t minimize your bow’s effectiveness by choosing too light of an arrow.
By Joe Bell
Most passionate bowhunters I know are serious shooters who love to participate in 3-D tournaments during the spring and summer months. In this game, shooting distances to life-like targets are totally unmarked. These events are challenging and loads of fun, and achieving a top score comes down to pure shooting ability and accurate guessing of the range. Those that consistently do well are not only talented shots but choose equipment most suited for the task—a super-accurate setup that drives an arrow at high speed. The reason for this is the fast arrow bales them out of minimal mistakes in distance judging and still allows a good “hit” on the animal.
Problem is, most of these shooters become so familiar (and confident) with this gear that they often use the same setup and arrow combination for their big-game hunting. Once they outfit these arrows with mechanical or low profile fixed-blade broadheads, they hunt. Most of their buddies are following suit, so it all seems like the way to go. I think this is a big mistake. Here’s why.
Where Energy Counts
If you bowhunt less-than-hardy animals, such as pronghorn antelope, blacktail deer or smallish whitetails, then your 330-grain 3-D arrow remains a sensible choice. I say screw on some proven broadheads, sight-in, and go hunting.
However, if you often target elk, big whitetails, or stocky mule deer and often consider shots at extended ranges, choosing a light and “speedy” 3-D arrow could potentially prove disastrous. A super-light arrow just doesn’t absorb a bow’s energy well enough, and you’ll need all you can get for big critters, particularly on downrange shots. Without sufficient energy, poor penetration occurs. Also, when I say “extended ranges,” I mean legitimate bowshots out to 40 or 50 yards.
It appears an arrow’s Kinetic Energy output is the fundamental way to determine its penetrating ability, minus the factor of broadhead selection of course. With that being the case, lets examine two arrows, a light vs. a medium-weight arrow, and see what the numbers conclude.
The Test: Light Vs. Medium-Weight Shaft
Using one of my setups, I shot two arrows through the chronograph—one weighing 343 grains, the other 426—weight difference, 83 grains. Both were spined correctly for the bow. Here are the arrow speeds and energy values.
The light arrow shot 279 fps, the heavier arrow 256 fps — a 23 fps difference. That’s a substantial difference and the faster arrow will no doubt make you a better shooter on the 3-D course.
However, lets plug in these arrow weights and arrow speeds into the kinetic energy formula, which is: Velocity (squared) x Arrow Weight divided by 450,240 = Kinetic Energy in foot-pounds.
The light arrow: 77841 x 343 divided by 450,240 = 59.30 foot-pounds. The heavier arrow: 65536 x 426 divided by 450,240 = 62 foot-pounds. The difference: 2.7 foot-pounds. Obviously, this is not significant, but even then the energy difference is close to 5 percent – and that’s measured right out of the bow!
But that’s not what this article is about. It’s about downrange energy—where it matters most in bowhunting situations.
Placing the same chronograph at the 40-yard mark, here were the arrows speeds, which we’ll then plug in to determine energy values.
At 40 yards, the light arrow traveled at 265 fps, the heavier arrow at 245 fps. The speed difference in the two shafts is nearly the same, however, the light arrow has slowed down 15 fps, compared to 10 fps of the heavier arrow, since the time of take off.
Though the light arrow is still flying in a fast and flat arch, it is losing energy and speed much more rapidly compared to the slower, heavier arrow.
Let’s compute the kinetic energy values at the 40-yard mark. The light arrow: 70225 x 343 divided by 450,240 = 53.49 foot-pounds. The heavier arrow: 60025 x 426 divided by 450,240 = 56.79 foot-pounds. The difference is now 3.3 foot-pounds, which equals about 7 percent more energy. The significance is going up, and it intensifies more and more as the distance increases.
When bowhunting the West, 40 to 50-yard shots are very common when pursuing mule deer, caribou and sometimes elk in open country. This 7 extra percent of penetrating energy can really save the day if you nick a shoulder bone, take an angled shot, or simply want two holes in the animal’s chest instead of one for better blood trailing and all around increased killing efficiency.
Also, our test here involves only a slightly heavier arrow—a light vs. a medium-weight shaft. Take this test to an extreme level and the energy differences become more significant. For example, when comparing a 500-grain vs. a 300-grain arrow, the difference in energy output is about 8 or 9 percent at 40 yards. At 50 and 60 yards, the energy output opens up to 10 percent or more.
Momentum and Angled Hits
Trying to shed some light on the factor of arrow weight and momentum, I did a test a couple years ago in which I shot a couple different arrows into a sheet of plywood. The plywood was positioned at a 60-degree angle and shot from 20 yards. Using various broadheads, it became obvious that a heavier arrow could make a difference on angled hits.
Each time, the heavier 450-grain arrow penetrated reliably whereas the lighter 340-grain arrow ricocheted off the board. Plywood is not an animal, but its rather rigid like a shoulder bone on a deer or elk, so some reasonable conclusions can be taken from this test. Although this examination was far from formal, it sure increased my confidence when using heavier arrow setups in the woods.
Beyond its capability to penetrate better, a medium-weight arrow yields other favorable qualities.
One important factor is “forgiveness,” and this holds true whether you use fixed or mechanical broadheads. There’s a good reason why indoor target shooters use the heaviest arrows and point-combinations spined correctly for their bows. The goal: create shafts that are as stable and forgiving as possible. The objective in this game is to hit the x-ring each and every time at 18 meters and these oversize, super-heavy 500 to 600-grain “logs” maximize this effort.
A heavier hunting arrow will shoot more forgiving and accurate for the same reason. Due to sheer weight and slower launch speeds, it is more stable and less likely to be “thrown” off target because of a minor release or follow-through flaw. I urge you to switch to a heavier arrow and do your own testing. Despite less-than-perfect archery form, heavier arrows seem to stay on target. This characteristic is especially useful when you’re faced with high-adrenaline, high-pressure shots in the field. A fast arrow may be a blessing on the 3-D range, but a slower heavier arrow counts for more in a tree stand when you’ve got the jitters and crunch time has arrived.
I noticed this forgiveness factor when doing the velocity tests for this article. My chronograph has a rather small 10-inch square-triangle-like shooting tunnel. At 40 yards, it looks about 5 inches wide. With the heavier arrows, I knew I’d thread the eye of the needle. With the lighter arrows, I had some twitchy doubts, though I got them all through. Still, mentally, it was different, and bowhunting is all mental.
Heavier arrows are quieter too. Go ahead and deck out your bow with all the latest sound-dampening accessories hoping for the quietest shot possible. But realize a heavier arrow will always emit a duller thud at the shot. This ultra-quiet thud could get you a second shot, just in case you need it. That’s a big deal.
Finally, heavier arrows, whether all carbon, carbon/aluminum or all-aluminum, are usually more durable and longer lasting. When you “slap” arrows together, ultra-light arrows tend to fracture easier, becoming a constant nuisance. Heavier arrows keep you less worried and shooting more, whether it is at targets or dirt clumps and stumps as you “plink” your way back into elk camp.
Go With a Medium-Weight Shaft
By bumping up arrow weight 75 to 100 grains, you gain a lot, as our downrange tests tell us. Yet, you still achieve a fairly fast arrow setup. This gives you the best of both worlds – a quick arrow that fly reasonably flat but hits hard when it arrives. And since a heavier shaft is potentially more forgiving and accurate, it makes a better choice when you might just get one shot during a hunt, or even for the entire season.
Light arrows may rule for 3-D shooting, but don’t make them your first choice for bowhunting magnum-size big game that simply require more downrange punch. By all means use light, accurate arrows during the spring and summer when 3-D tournaments are a great way to sharpen your archery skills. But be wise and make the switch back to a more reliable heavier arrow setup. As long as you give yourself a month or two of time familiarizing yourself with this slower setup’s trajectory, you’ll find yourself no less confident come hunting time.
Besides, your laser rangefinder will tell you the exact distance to your buck or bull on 90 percent of your shots. From here the job is simple—execute a good shot. Your “beefy” arrow choice will take care of the rest. The numbers tell us so.
(camera graphic) Joe Bell
The author shot this Sitka blacktail deer straight through the onside shoulder blade. Despite this, his 400-grain arrow setup penetrated completely, downing the animal quickly.
Slightly heavier arrows are, on average, more accurate. The author shot this three-arrow group from 55 yards using a BowTech Guardian and Easton AC Super Slim 390-grain arrows.
Bell believes heavier arrows are more forgiving to shoot, particularly in the field when adrenaline is flowing. He made a precise 35-yard, quartering-away shot on this javelina using a 425-grain arrow, despite a slight “rushed” pluck of the string using a fingers release.
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