The Truth About Open-on-Impact Broadheads

Open-on-Impact Broadheads

Mechanical broadheads are making news. These hunting aids, sometimes referred to as open-on-impact heads, are now legal to use in most states and have become widely accepted by many bowhunters.
A huge variety of mechanical broadheads are available to the bowhunting public. In fact, most of the major broadhead manufacturers offer a mechanical design. Of the many brands and models currently available, all mechanical heads feature blades that are partly or completely encased by the ferrule of the broadhead during flight. When the broadhead contacts its target, the blades open using one of three different blade deployment methods.

Improved arrow flight is the primary advantage of mechanical broadheads. Because little or no blade surface is exposed to the air in flight, arrows equipped with mechanical broadheads fly like they were outfitted with target points. Hunters who shoot very fast bows will no doubt enjoy the greatest benefit from mechanical heads. At arrow speeds above 250 fps, it becomes increasingly difficult to achieve consistent broadhead flight with fixed-blade broadheads.


On the flip side, mechanical broadheads also have some disadvantages, the most pronounced of which is a reduction in overall arrow penetration. Because some of the kinetic energy is used up to deploy the blades, mechanical heads often don’t deliver the penetration users of fixed-blade broadheads have come to enjoy. This is especially true of mechanical heads that feature very large cutting diameters.

Mechanical Broadhead Styles

Some of the earliest mechanical heads incorporated a retracting nose cone that when pushed in forced the blades to open. Examples of this style of mechanical broadhead include the Puckett Bloodtrailer and Finished Archery Systems Auto Clearcut.

Other broadheads use an “O” ring or rubber band to hold the blades in place during flight. The rubber band simply rolls out of the way on impact, allowing the blades to swing open. This method of holding the blades in place seems to be the most popular and is currently used with the Rocky Mountain Assassin, Wasp Jak-Hammer, Game Tracker Stiletto, Mar-Den Vortex, Satellite Scorpion, Rocket Miniblaster, and many others.

The third style of mechanical broadhead holds the blades in place with a friction fitting that allows the blades to cam open upon impact. Manufacturers using this method include the Golden Key Deadhead Dagger, New Archery Products Spitfire, Gold Tip Gladiator, and Rocky Mountain Gator.

Narrowing Down the Options

It’s nice to have a large selection when picking out archery equipment, but with selection comes the problem of deciding which models to try. Unfortunately, mechanical broadheads are very expensive. Be prepared to pay at least two or three times as much for mechanical heads as the fixed-blade models you’ve come to trust.

I’ve had an opportunity to test many of the mechanical heads on the market. Since 1994 I’ve harvested whitetail deer, caribou, and even black bear with mechanical heads. Of the dozen or so animals I’ve taken with mechanical broadheads, none failed to open on impact. I’ve also been involved in another dozen kills by other hunters with similar results.

Call me skeptical, but before I took my first mechanical broadhead into the field I shot many models into foam targets, blocks of plywood, old telephone books, and other targets just to see what would happen. With the exception of a few blades being sheared off or bent, the mechanical heads I’ve used functioned much as advertised.

An advocate of fast bows and the flat trajectory they provide, I’ve come to embrace the open-on-impact broadhead as a deadly alternative to the fixed-blade broadhead. However, in experimenting with these heads I’ve also discovered that a serious loss of penetration can result depending on the model used, the bow’s peak draw weight, arrow shaft stiffness, and the nature of the arrow impact.

Arrow penetration is a critical element of bow hunting, yet many hunters never give this issue a second thought. I personally believe that every hunter should strive to use an arrow/broadhead combination that delivers pass-through penetration regardless of shot angle.

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Most hunters would agree that peak bow draw weight is the most significant factor controlling overall arrow penetration. In my experience at least 60 pounds of peak draw weight is required to insure pass-through penetration. This observation is based on deer-size game when using mechanical broadheads. Young hunters, women, or others who pull less than 60 pounds are probably wise to stick with a fixed-blade broadhead.

Broadheads that feature a very large cutting diameter should also be avoided unless a heavy draw weight is used. Some open-on-impact heads cut entrance wounds that measure over 2-3/4 inches! With such a huge entrance wound, it’s easy to see why penetration is limited. Friction caused when the blades cut huge amounts of tissue can significantly reduce overall penetration. Also, with large cutting diameter models the likelihood that the blades will contact bone and be stopped or slowed down is greater than with smaller cutting diameter heads.

Huge cutting diameter broadheads appeal to many hunters who rationalize that a large entrance wound will yield a strong blood trail and put the animal down quicker. Perhaps, but I’ve never seen any research that would substantiate this claim. Furthermore, in my own field experiences this hasn’t been the case. The size of the entrance hole means little. What’s important is hitting the animal in a vital location and achieving both an entrance and exit wound.

Broadhead penetration is also influenced by shot angle. On broadside shots achieving lethal penetration isn’t nearly as critical as on quartering away shots. Bowhunters must take into consideration the shot angles they expect to encounter before selecting a broadhead.

Arrow shafts play a significant role in broadhead penetration. All arrows flex upon impact, robbing the arrow/broadhead combination of valuable kinetic energy. Stated another way; a stiff arrow shaft delivers the best broadhead penetration. A stiff arrow shaft acts to concentrate energy at the broadhead where it’s needed most.

Graphite arrows are up to five times stiffer than similar aluminum shafts. Graphite arrows provide the ultimate in penetration when using mechanical heads. Graphite/aluminum composites like the ACC are stiffer than aluminum and also make an excellent choice for use with mechanical heads. Many of the popular aluminum shafts are simply too thin-walled to provide adequate penetration with mechanical heads. This is especially true of the popular “super lites” including the 2212, 2213, 2312, 2314, 2413, and 2512.

Arrow shaft stiffness can also be influenced by shaft length. Shorter arrows such as those used with overdraws are stiffer than full-length arrows and deliver better broadhead penetration.

The blades on broadheads can also influence overall performance. Thicker blades are less likely to bend when impacting hard bone and tissue, resulting in a clean cut and deeper wound channel. The blades on mechanical heads range from .025 to .040 inch thickness.

Summing It Up

Hunters who are interested in trying mechanical broadheads can achieve outstanding results so long as they follow these simple guidelines.

  • Match mechanical broadheads with bows shooting at least 60 pounds of peak draw weight.
  • A modest cutting diameter penetrates better and yields quicker kills than a large cutting diameter.
  • Match them with graphite, graphite/aluminum composite, or thick-walled aluminum arrows.
  • Thick blades are less likely to bend or twist; twisted blades result in reduced penetration.
  • Strive for broadside shots whenever possible, avoiding poor shot angles and shots beyond 40 yards all together.

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