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Penetration Factors... Bows, Broadheads and Arrows

Over twenty years ago I harvested my first deer with a bow. At thirty yards, the Bear Whitetail compound had ample force to drive the wooden shafted, two blade Bear broadhead, to a near pass through. The nice 5 x 5 buck went less than seventy yards; I was hooked on bowhunting for life.



Although I started with wooden shaft arrows and a 4-wheel bow, I was able to get a true flying arrow that optimized my equipment's performance.



Today's bowhunter is inundated with high tech, high speed bows, state of the art broadheads, and superior quality, unbendable arrows. This makes our choice much easier in selecting a set-up that will perform to our hunting needs. Each of these will independently help increase the penetrating ability and our overall performance, but when combining the three to make a set-up for optimal performance and penetration, many questions are raised..



So what is the most important factor for penetration? This is a hot topic in today's media and if we ask ten different bowhunters, you would probable get ten different opinions.



Let's look at the primary factors that have the greatest effect on penetration. These are: Kinetic Energy - (Bows), Broadhead Sharpness and Arrow Flight.



Each of these encompasses a broad category and each is a topic in itself, but by evaluating them individually, we can make a better judgment of what our needs will be for the game we pursue.



Most bowhunters would say Kinetic Energy (KE) is the most important factor in arrow penetration. While I agree that it is a very critical aspect, with today's modern equipment it really becomes a moot point. Let me explain.



Kinetic Energy... Kinetic Energy is defined as the amount of energy an object has while it is in motion. For our usage, it is measured in foot pounds (ft-lb) and is calculated by Velocity x Velocity x Arrow Weight / 450,240.



The chart below lists the recommendations of ft-lbs. for each specific sized animal. Although there are minimums for each, many animals have been harvested with below minimum ft-lbs. I know of several bowhunters, (my wife included), that have taken deer with less than 35 ft-lbs. of energy. She shot a deer with an arrow weighing 420 grains traveling at 180 fps. This gave her a KE value of 30 ft-lbs.; this arrow past through the deer.



Kinetic Energy - Hunting Usage
< 25 ft-lbs. Small Game
25-41 ft-lbs. Medium Game (deer, antelope, etc.)
42-65 ft-lbs. Large Game (elk, moose, black bear, etc.)
> 65 ft-lbs. Toughest Game (cape buffalo, grizzly, etc.)



 

The modern bow has taken on a new design. Manufacturers are developing uni-cam systems, more parallel limbs, weighted cams, vibration dampeners and lighter weight bows, making them more energy efficient than ever before. At almost all draw weights, these bows carry enough energy to meet industry recommendations of maintaining sufficient penetrating force - KE. An example of this is most name brand bows taken from the store shelf and set-up with a 50 pound draw weight, will cast an arrow of 450 grains a minimum of 215-220 fps. This gives you a KE of 46 ft. lbs. By most manufacturer standards, this is enough to pass completely through a deer. (50 ft. lbs. will allow complete pass through of an elk) So although KE is a primary factor in penetration, it becomes a very small tool of adjustment when attaining optimal penetration.



 

The modern bow has taken on a new design. Manufacturers are developing uni-cam systems, more parallel limbs, weighted cams, vibration dampeners and lighter weight bows, making them more energy efficient than ever before. At almost all draw weights, these bows carry enough energy to meet industry recommendations of maintaining sufficient penetrating force - KE. An example of this is most name brand bows taken from the store shelf and set-up with a 50 pound draw weight, will cast an arrow of 450 grains a minimum of 215-220 fps. This gives you a KE of 46 ft. lbs. By most manufacturer standards, this is enough to pass completely through a deer. (50 ft. lbs. will allow complete pass through of an elk) So although KE is a primary factor in penetration, it becomes a very small tool of adjustment when attaining optimal penetration.



Broadhead Sharpness... In bowhunting, the killing is done by causing hemorrhaging, so optimally we want razor sharp broadheads that create the greatest amount of blood loss, for a quick, humane harvest. We can assume that the blood loss is increased with more blades or a larger cutting diameter broadhead. While this is true, some hunters feel that increasing the number of blades and cutting diameter causes an adverse effect on the broadhead penetrating ability; this adverse effect is very minimal. It is the sharpness of the broadhead that creates the blood loss and a sharp broadhead will always penetrate further than a dull one - PERIOD.



Now is the question of which broadhead?



The energy efficiency of modern bows has made this answer quite easy...Choose the one you are confident with and that shoots good groups for you. Remember, broadhead sharpness is what is important here, not broadhead type. Whether you choose mechanical or fixed blade, conical point, chisel point, or leading edge cutting point, make sure they are sharp and fly true. You have heard of many different kinds of tests to factor which of these styles of broadheads penetrates best, but none can duplicate the actual animal tissue and lubricating ability of blood and body fluids. Each broadhead tip and cutting style will pass through a deer if all the primary factors of bow kinetic energy and arrow flight are met.



If you are choosing to shoot mechanical broadheads, there are several things you should note. Some states do not allow the use of mechanical broadheads, while others have a restriction on using them for large game such as elk or moose. Also, some outfitters do not allow the use of mechanical broadheads in their camps. Be sure to check the state regulations and the outfitter you may be hunting with.



Keeping them sharp... If you are a traditional person who likes to sharpen his or her own broadheads and they fly well for you, then by all means do so. I have enjoyed sitting around camp watching these bowhunters take pride in putting a razor's edge on their broadheads. I was never patient enough for this and like most bowhunters have chosen to use the replaceable blade broadhead. Always remember to check the tip of your broadhead and the straightness of the ferrule when replacing blades. Tips can be sharpened with a small file, and spin checks can be done to check if the ferrule or tip has been bent. After replacing the blades on my broadheads, I will place the tip on a hard surface or in the palm of my hand and watch for any wobble as I spin them. If there is any noticeable bend, I mark them and use them for practice arrows.



Whichever you prefer, they must be SHARP!



Whichever you prefer, they must be SHARP!



Arrow Flight... Probably the most complicated, but I feel the most important factor in penetration, is Arrow Flight. When all the variables are the same you gain the most penetration with a straight, true flying arrow. A set-up that is correct in arrow weight and arrow length will achieve the greatest penetrating ability.



When an arrow leaves the bow it will flex in a serpentine-like fashion, then straighten and fly true at 10 to 15 yards. This flexion absorbs energy, thus it decreases the arrows penetrating ability. This unstable arrow also creates more friction when penetrating, also decreasing penetration. Some graphite/carbon arrow designs help control the arrow flight and make it fly true at a shorter distance. Any excessive flexion or nock-end arrow wobble due to over or under spined arrows, fletching hitting the rest, poor release or poorly tuned bow, will absorb energy and have a negative effect on penetration. This is why a properly tuned bow and true flying arrow are so important. Our goal is to limit the amount of flexion, yet have an arrow stable that can control the broadhead to achieve good flight.



 

Guidelines to achieve optimal arrow flight:
 


  • Make sure your bow is properly tuned. Most local pro shops can tune and set-up your bow for the correct draw length and properly spined arrows. Correct arrow size can also be found on Easton arrow charts. If you are purchasing a new bow, shoot them before buying. Not all bows are easy to shoot. For hunting purposes, consider a bow with a longer brace height. This will make it more forgiving and easier to achieve good arrow flight.

     



     

    Guidelines to achieve optimal arrow flight:
     


    • Make sure your bow is properly tuned. Most local pro shops can tune and set-up your bow for the correct draw length and properly spined arrows. Correct arrow size can also be found on Easton arrow charts. If you are purchasing a new bow, shoot them before buying. Not all bows are easy to shoot. For hunting purposes, consider a bow with a longer brace height. This will make it more forgiving and easier to achieve good arrow flight.

       



       

    • Paper tune your broadheads. Paper tuning is when you shoot broadheads (or field points) through a tightly stretched paper at a distance of 8 - 10 feet. By analyzing the tears made by the broadheads, you can determine if your arrows are over or under spined, if nocking points need to be changed, or if you need to use heavier or lighter tips (broadheads). This is one point where bowhunters should be open-minded about adjusting the draw weight to obtain optimum flight. Often times slight adjustments in draw weight will make the arrow fly true. This is because a balance can be reached between the draw weight and the arrow spine. Note: Not all shooters and set-ups will attain a perfect hole when paper tuned. Slight deviations in the broadhead holes are acceptable. Tear charts can be found at local pro shops and are in most bow manuals.

       



       

    • Practice form and release. Both mechanical release shooters and finger shooters need to practice good form and follow through. At the archery range, have your shooting partner watch your form and follow through after the shot. Small adjustments in stance or hand grip can make the big difference in arrow flight.

       



       

    • Practice with Broadheads. Broadheads will not always fly and hit the same as your field points, including mechanical broadheads. Note: Fletching can be the deciding factor for arrow flight with broadheads. Feather fletching, while lighter in weight, will create more drag thus more arrow stabilizing. Using a 4-5 inch fletching will also help in stabilizing arrow flight.
       

    Other factors to keep in mind for penetration:

    • Shot placement. Striving for a broadside shot is very important. This gives you the best opportunity at a double lung, pass through shot and a prospect for a good blood trail. A poor hit is a poor hit, no matter what broadhead or set-up you have.

       



       

    • Size of the animal. If you're going after large game, such as moose, elk, or black bear, make sure your equipment is set-up for the recommended specifications. In this way if a poor hit occurs, you have a better chance at recovering the animal.

       



       

    • Moving target or steep angles. Deflection of an arrow hitting a moving target causes more friction and steep angles will have a larger body part to penetrate. Both of these can decrease optimal penetration.
       

    Keeping all this in mind is very difficult, but by starting with the basics and building a strong foundation of knowledge and fundamental skills, you will get the most out of your equipment. Now all you have to do is put the arrow where it counts.

     



    As I have evolved from a beginner to novice to experienced bowhunter, so has my equipment. With the increased knowledge, time and experience, my bow has changed from that Bear Whitetail with wooden arrows to a state-of-the-art Mathews ICON bow, graphite Gold Tip arrows, and replaceable blade Rocky Mountain Broadheads. By following the guidelines I have listed, I have combined these into a set-up that is well-rounded for all my hunting needs.



    The overwhelming choice in today's market oftentimes creates more problems than answers, and more controversy than communication. But by talking to the bowhunting specialists at local sporting goods stores, joining local archery clubs and inquiring into web sites such as Fishing Buddy Outdoors, you can attain the expert advice to get the success you desire. Remember: Success = Preparation Meeting Opportunity.



    Editor's Note: Wayne Muth is a dedicated archer and has become a well rounded bowhunter throughout his archery career. He has had the opportunity to hunt and harvest various species of animals and it is his ability to maximize his equipment to the best of its capabilities that has helped to make him successful in the field. His knowledge has gained him respect from his peers and his words have graced the pages of some great bowhunting magazines.



     
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Posted On: 10/15/2004 00:00 AM
1318 Views, 0 Comments

Tags: broadheads, broadhead, bows, penetration, bow, bear, pass, deer, factors.., arro
More Tags: Wayne Muth, energy, uni-cam systems, archery, bow kinetic energy, high tech, energy efficiency, dedicated archer, Editor,
Region: North Dakota

Categories: Hunting > Big Game Hunting - Bear, Elk, Moose, Antelope
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