Five Ways to Increase Penetration

February 9th, 2009 / Posted by
Five Ways to Increase Penetration

By Bill Winke

It is a reality that despite our best intentions and efforts, not every animal we shoot at will be double-lunged and fall within sight. Blood trailing is a part of bowhunting, and with plenty of blood sign to follow, the odds of finding the animal quickly are much improved.
The vast majority of bowhunters pursue whitetails from tree stands. Many of the shots taken this fall will be at ranges of 10 yards, or less from stands 15 feet or more above the ground. Such shots create a sharply downward angle for which an exit hole is critical to the blood trailing process. It takes a hunting outfit set up with penetration in mind to do the job under these conditions.

On a marginal hit the most important thing is penetration. There’s no such thing as too much penetration. I hit a nice eight- pointer a few years back right through the lower part of his shoulder. I wasn’t planning to hit him there, but I did. My arrow not only cut deep enough to punch both lungs, it actually passed all the way through the buck and was laying on the ground on the other side. That’s one trophy that may have gotten away (the trailing process would have been much tougher with a single-lung hit) if I hadn’t been thinking penetration when I put my hunting rig together. I was shooting a heavy draw weight bow and conventional fixed-blade broadheads.

Increase Your Draw Weight

For every pound you increase your draw weight your penetration energy increases by approximately 1 ¾%. You can see that a couple of pounds may not make a big difference, but five pounds, or more, starts to have a significant effect.

Sharply downward shot angles make it more difficult to achieve full penetration unless you select your hunting rig with care. An exit hole under such conditions is important to the quality of your blood trail and the ease of recovery.

Sharply downward shot angles make it more difficult to achieve full penetration unless you select your hunting rig with care. An exit hole under such conditions is important to the quality of your blood trail and the ease of recovery.

Shoot the heaviest draw weight you can handle accurately under all hunting conditions. There are many different standards floating around to help bowhunters determine their maximum accurate draw weight. One says to shoot the highest weight you can draw without having to raise your bow arm above parallel when you yank the string back. Another recommends the maximum you can draw sitting down flat on the floor with your legs out in front of you. I personally believe you shouldn’t shoot a bow that you can’t hold at full draw for at least a minute without shaking. Regardless of how you achieve your maximum draw weight; make sure to get in plenty of practice before and during the season to keep your shooting muscles strong.

Increase Your Arrow Weight

With all the unfounded hype surrounding arrow speed vs. penetration, it’s no surprise that many bowhunters believe dropping their arrow weight by 50 grains to pick up 10 extra feet per second is killing their penetration energy. In truth, a heavy arrow does absorb more of the bow’s energy when you release the string, giving it more in-flight (kinetic) energy, but the differences are much less significant than you may have been led to believe.

Based on efficiency studies performed on various bow styles shooting mid-weight arrows, (450 to 600 grains) a 50 grain reduction or increase in arrow weight results in a corresponding change of roughly 1 to 1 ½% in penetration energy. To pick up any real advantage by increasing arrow weight you would need to bump it up dramatically – to the tune of several hundred grains!

Even though the goal of this article is to look for ways to increase penetration, we shouldn’t overlook the important fact of knowing where not to look for it. Unless you’re already shooting light arrows, (under 450 grains) to give up 10 fps for only a one percent increase in penetration is a mistake.
Tune Your Bow Perfectly

In addition to being more accurate, arrows that fly perfectly penetrate better than those that slash their way to the target. When the arrow hits an animal with all its momentum directed right down the shaft, as it does when flying straight, penetration is maximized. Plus, straight flying arrows carry their speed better down-range, which also improves penetration.

For a quick reference on how to tune your bow, refer to edersbow archives and search under the key word “tuning”. For a comprehensive study on the subject of tuning, request Easton’s Arrow Tuning and Maintenance Guide. (There is a $2.50 charge for this 32 page brochure.)
Experiment With Different Shafts

Several years ago I witnessed testing conducted by AFC Carbon Arrows (before the product line was sold to Game Tracker) in which a couple of interesting outcomes were noted. Carbon arrows and aluminum arrows of exactly the same weight were both tuned and shot from a shooting machine at various distances into a wide variety of materials including sand, ethafoam and even beef livers. In all cases the carbon arrow penetrated more deeply (as much as 25% more) than an aluminum 2312 of the same weight.

How this correlates to performance on live animals is still inconclusive. No one has been able to perfectly duplicate the conditions of actual penetration on game in a controlled test environment. It is logical, however, that smaller diameter shafts would penetrate better than larger diameter shafts in many different mediums due solely to their reduced surface area. I’ll leave it you to arrive at your own conclusions as to whether carbon out-penetrates aluminum in real live game.

For what it’s worth, the test also showed that 40 yards down-range the smaller diameter carbon arrows retained about 1 ½% more of their initial velocity than did larger diameter aluminum arrows of the same weight.
Use The Best Penetrating Broadheads

We can shoot all we want into foam bales and measure how far the broadheads bury, but foam isn’t the same as an animal’s shoulder. Unfortunately, tests using foam and other inanimate materials are all we have to work with, so we have to make the best assumptions we can based on the information available.

All else being equal, broadheads with small cutting diameters penetrate more deeply than heads with large cutting diameters. It is purely a matter of the amount of tissue contacted. Heads having blades with a low angle have the potential to penetrate better than heads with a high blade angle and the same cutting diameter. In most cases, two- bladed heads will penetrate better than three-blade (or more) heads of the same cutting diameter. Under the majority of conditions, mechanical heads don’t penetrate as well as fixed-blade heads. And cut- to-point broadheads have been shown in testing I’ve seen to out- penetrate all other styles.

In other words, if you want a broadhead that promotes better penetration try any combination of the following styles: fixed- blades, fewer blades, cut-to-the-point designs and/or a smaller cutting diameter.

Penetration is an important part of equipment selection, even if all you hunt are whitetails. By doing all the things listed here you’ll greatly increase your penetration on game. An exit hole will be more likely on downward shots from tree stands and your chances for making a clean kill should you hit your buck of a lifetime in the shoulder could not be better.

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