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Arrow penetration- How much is enough? Bring up arrow penetration in deer camp this year and you are probably going to get an earful of opinions about the subject. In reality though given today's modern archery tackle it is not really a concern for the average bowhunter. The age-old arguments about which broadhead or arrows penetrate better are generally pure speculation or one person's perception based on their personal experience. There are four crucial factors in determining the penetration of a specific set up. They are broadhead type or style, arrow flight, friction and last but not least is kinetic energy. Broadhead type- Discussion about which broadhead is the best have been known to become heated battles among bowhunters. When shooting various styles into a foam block the traditional cut to tip head penetrated deeper than the popular chisel point three-blade head. The difference will be how much farther one sticks in the ground than the other after making a good shot. The popular expandable heads penetrate the least in the foam block in comparison to the fixed blade designs. Yet every year literally thousands of deer are taken using them. Arrow Flight- Arrow flight can effect your penetration in a big way. If you are getting perfect arrow flight, all the stored energy in the arrow is placed directly behind the broadhead thus assisting the penetration. If your arrow is sliding tail left or right you may hit where you aim but you are not getting the maximum energy stored in the shaft. Perfect arrow flight is especially important when shooting a mechanical broadhead. Friction- Friction is the drag on a particular arrow/broadhead set up during penetration. A larger diameter Easton 2413 will have more "drag" or friction than an ACC 3-49 will because the ACC is so much smaller in diameter. Broadhead design will also increase or decrease friction. A traditional style head with a cut to tip point will have less friction than a chisel point as the chisel point will have to blow through the hide or rib before the blades can cut. The difference is minimal at best. On the expandable heads there is even more friction as the chisel point must bust through, then the blades must open before you can reduce friction by letting the sharp blades do their job. Kinetic Energy- Kinetic Energy or KE is the single most important factor that effects arrow penetration. To calculate your KE you must first know your arrow speed in feet per second, this is your velocity, and your arrow weight in grains. The formula is Velocity X Velocity X Arrow weight Divided by 450240. Since the boom of carbon arrows with their faster and more durable characteristics KE has become even more important. A carbon shaft is in fact lighter and faster but the loss of weight can have an effect on your KE. For example, an aluminum shaft that weighs 499 grains traveling at 270 FPS generates 80.79 foot pounds of KE. A carbon shaft of the same length shot out of the same bow will weigh around 396 grains and travel 285 FPS. This arrow generates 64.44 pounds of kinetic energy. On the surface it looks dramatic but in reality Easton recommends 24-41 foot Pounds of KE for deer sized game, 42-65 for elk, black bear and wild boar. You can draw your own conclusion about KE. The only area of concern is the use of carbon shafts with expandable heads. Generally speaking most mechanical heads need at least 50 lbs of KE to function properly as a tremendous amount of your KE is used to open the blades. The bottom line is that a modern bow, arrow and broadhead in the hands of a competent bow hunter will take most deer sized game with total pass thru shoots. The real key is shot placement, by only taking those high percentage shots an archer should have no problems. No amount of KE will ever make up for a poor shot or an accidental hit on a major bone. Hunt safe, hunt hard and always wear a fall restraint device when hunting from a tree stand. *Troy Basso is a freelance writer and instructor for the National Bowhunter Education Program.
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