Facts About Arrow Penetration
Updated: Jan 8, 2022
Driving your arrow deep will ensure a quick kill and better blood trail. Here are several ways to accomplish maximum penetration.
Myths about arrow penetration fly around hunting camp. Some topics are debatable. Others are so silly I shake my head. Bowhunters have always argued about tactics and gear, and I’m sure they always will. Penetration is an old standby for debate, and an interesting one to think about in your spare time.
One of the least productive penetration arguments says that your arrow should stay in the animal. This line of thinking relies on two huge misconceptions.
First, how can anyone deliberately retard arrow penetration? The best-laid plans seldom work out. For example, one traditional recurve-shooting friend of mine decided to shoot a 40-pound bow last year with lightweight carbon arrows. The hope was that he’d leave his arrow inside a deer to create more cutting action. The first buck he hit got away clean after the arrow bounced off the shoulder blade. The second deer he hit dropped fast, but not because the broadhead stayed inside. The light, low-energy shaft sailed between ribs and completely out the other side. So much for controlling penetration.
I believe this debate is absurd, in part because nobody can count on shallow penetration. Furthermore, I cannot buy the idea that poor penetration is ever good. A full-size, shaving-sharp broadhead cuts an awesome hole as it slices through a animal’s chest, and it need not stay inside to cause a quick death. The damage has already been done. If the arrow does fail to exit, a number of not-so-good things can occur.
For one thing, no exit hole means less blood on the ground. Trailing can be difficult, even if your animal is done for. Give me two holes in a deer, elk, or bear every time!
Less broadhead penetration also means less tissue damage and a slower kill. An arrow that stays in your deer will also wave like a flag as the animal runs off, scaring it badly as it feels the shaft and sees it in the corner of its eye.
And then there’s the added problem of hitting leg, shoulder, spine, or hip bone with a setup designed for shallow penetration. A high-energy arrow will often kill with such marginal hits. A low-energy arrow in these same places might cripple but fail to kill.
How could anyone seriously promote less arrow penetration when the upshot is often less broadhead damage to the critter, slower blood flow to the ground, and a faster and farther running panicked animal? It beats me.
Modern bows are potent shooting tools. An average 60-pound compound today produces at least 60 or 70 foot-pounds of point-blank penetrating arrow energy, even with a fairly lightweight shaft. That’s 20 to 30-percent more power than a 60-pound compound produced just a few decades ago, and an even higher percentage above most 60-pound recurve bows or longbows. Such energy at your fingertips makes arguments about arrow penetration in medium-size game like whitetails less passionate than they used to be, because bowhunters shoot completely through most broadside bucks. Penetration can be more of an issue in larger game like caribou, elk, and moose.
But no matter what the species, there are other factors that often affect arrow penetration in quartering or poorly hit game. Thoughtful bowhunters milk every last ounce of “oomph” out of their setups, just in case they score a less than perfect hit.
There’s no secret to getting more penetration. The hardest way is cranking up bow poundage. A five-pound increase in compound peak weight will yield about 10-percent more penetrating arrow energy, but there’s a price to pay. The bow will be tougher to draw and aim.
Two methods make more sense, because they don’t overburden your shooting muscles.
If you increase arrow weight 50 grains, you’ll gain about 1-1/2-percent more penetration at close range and up to 4 or 5-percent beyond 40 yards. This is a fact of physics, and has been tested many times. Some carbon arrow companies say that very small-diameter shafts penetrate better in game, but such claims can be misleading. A skinny carbon shaft is heavier than a fatter carbon shaft of the same spine (stiffness), so the skinny shaft certainly absorbs more energy from your bow and drives deeper in game. But in my experience, diameter alone seldom affects arrow penetration in an animal because the broadhead cuts a much larger hole than the size of the shaft. Unless it drives directly through bone, the shaft slides along behind in the broadhead channel with fat, blood, and other body fluids lubricating its path. Large or small, the shaft encounters almost no penetrating resistance.
Penetration through bone is another story. The larger the shaft, the more pressure bone can exert as the arrow drives through. In extreme cases—such as when an arrow splits the rib of a moose or bison—I have seen bone actually flatten the sides of an aluminum shaft as the arrow wedges through. But with most shot placements, I believe the difference between fat and skinny hunting shafts tends to be overblown by manufacturers.
Broadhead design can be the single biggest “free lunch” when it comes to penetration in game. Cranking up your bow gives you some extra penetration. Shooting a heavier shaft gives you a little bit more. But using a streamlined, low-friction broadhead can boost penetration a huge amount. Heads with cutting noses or small pyramid points drive deeper through all flesh-like substances including green cowhides, layers of tanned leather, and dead animals. Some companies use foam, ballistic gelatin, or other synthetic substances to test the penetration of broadheads or arrow shafts, but most such mediums clamp around the shaft during penetration and produce bogus results. In my experience, only animal-like substances give true readings about penetration in living game.
By comparison, high-friction heads like some designs that open on impact or incorporate large nose cones can absolutely destroy deep penetration. Mechanical broadheads with very large “footprints”, say 2-1/2” wide when open, will certainly increase penetrating friction. Exact broadhead design, width when open, and angle of blade edges all factor into performance. In deer-sized animals, mechanicals can be awesomely deadly from any modern bow. In critters over 700 pounds, reduced penetration might be a factor in killing ability.
I have had great results on elk and other magnum-sized animals with broadheads like the G5 Striker V2, Striker X, or Montec because these are streamlined and also stout for incredible penetration. An often overlooked factor in penetration is the strength of the head you use. For example, a Striker or Montec will drive through flesh and bone without bending or breaking, while other broadhead designs with weak aluminum ferrules or thin blades can crumple or shatter on impact. This will severely retard penetration and tissue damage, and might lose an animal.
Bowhunters worth their salt know broadheads must be shaving sharp to cleanly slice through vital flesh for a quick kill and best blood trails. But I believe that truly keen edges also penetrate better than those that are not so sharp. For killing ability and best penetration, be sure to check all broadhead edges before you hunt. One easy way is shaving a little hair from your arm. Another is stretching a rubber band between two fingers and sliding an edge across the band with light pressure. A correctly honed edge—factory sharpened or done by yourself—will instantly cut through the rubber band without any drag.
Never bowhunt with dull broadheads!
Poorly flying, badly tuned arrows that wobble through the air can ruin deep penetration. Drag against flesh and bone is high, and blades that open on impact or arrows that wobble can also flip the arrow sideways with angling hits. This is called “cartwheeling.” Even hunters using heavy-draw bows don’t always get arrow pass-throughs on perfectly broadside deer if arrows flip or create high friction. If you don’t believe this, ask a few veteran hunting guides about their experiences with head designs like mechanicals. Most swear at high-friction heads, and some refuse to guide hunters who use them…especially on larger animals like elk.
Modern archery gear is more than powerful enough to blow through the biggest animals on our continent. But you’ve got to do your part. Tune arrows for perfect flight, and maximize penetration with draw weight, arrow weight, and streamlined heads. If your animal jumps the string, if you make a poor shot, or if you go after a magnum critter like a moose or bison, you’ll be grateful for extra penetration.