Broadheads - whats the difference
Types of broadheads.
Every year Manufacturers develop new models to maximize cutting efficiency, reduce flight deviation and maximise impact stability, even if you're happy with the broadheads you shoot, it might be worth considering the new broadhead options.
Fixed blade, and Mechanical (or expendables) blade.
Broadheads are divided into 2 categories which are based on their physical makeup, and also the number of blades they have. These two main categories are fixed blade, and mechanical blade.
Within those main categories, you will find sub categories. Various designs bridge the basic model descriptions by adding features like chisle tip and cut-on-contact blades on the tip.
I find that bowhunters decisions on broadhead selection is a matter of personal preference that bares out from experience, the speed of the hunting arrow and the game being sought. If you're new to bowhunting and would like some insight into the options, here is our guideline.
Rough Selection Guide
Generally bowhunters with lower shooting speeds created by lower poundage bows, are better off using fixed-blade broadheads of 1 & 1/4” cutting width or less. The small diameter hunting broadheads improve penetration. Also give additional consideration to selecting a cut-on-contact broadhead. Cut-on-contact broadheads have minimal resistance, which increases penetration.
Bowhunters with higher draw weights and faster speeds have more options. Increased kinetic energy gives the advantage of using larger-diameter fixed-blade or mechanical broadheads. With good penetration larger broadheads have good potential to produce heavy blood trails, but there is a point of diminishing returns. Often very large blades should be reserved for smaller game such as turkeys when penetration isn't an issue.
The number of blades that a broadhead has will have a direct impact on maximising tissue damage giving a faster kill and better blood trail. With more blades producing the best effect. The theory is that with broadheads using three or four blades, at least two are cutting across the grain of muscle tissue, making it less likely you’ll lose a blood trail because of muscle fibers closing up a cut that happens to run with the grain.
The blades can be removed to sharpen or replace, on a few options the points are replaceable.
Full-blade broadheads with sharp blades that extend from the tip of the broadhead to the rear of the blades. One piece broadheads come in two-blade, three-blade and four-blade versions.
Have blades that fold into the body to reduce drag and deflection during flight. The cutting blades extend upon penetration and give these heads their name.
Fixed-blade broadheads roughly fit into 2 types, one-piece broadheads and those with replaceable blades. Replaceable-blade broadheads are very popular because you don’t have to deal with the tedious process of sharpening the blades’ edges. When they lose their edge, you simply drop in a new razor-sharp blade.
Within these types there are 2 blade, 3 blade and 4 blade configurations. For new bowhunters not as experienced in bow tuning, smaller diameter and fewer blades would be worth considering when it comes to broadhead selection.
A poorly tuned bow will have a greater effect in the flight of a hunting arrow when it leaves the rest. As an example , a hunting arrow that leaves with its fletching end too high will tend to catch the wind and dive low in its trajectory. Conversely, when the fletching end is too low on release, the angle will cause the blade to catch the wind and plane upward.
The number and size of blades will increase this effect the bigger they are the more planing suface. Compact broadheads and their smaller surface area reduces the reffects of wind and out-of-tune bows compared to large broadheads. Most manufacturers offer at least one compact fixed-blade broadhead.
Leading Edges - Chisel Tip vs Cut on Contact
Broadheads that use a chisel tip will punch through an animal's tough hide opening the tissue for the broadhead's blades to cut. This ensures the broadhead enters the animal at the desired angle without altering the trajectory. For durability Chisel tips are excellent broadheads, and are well known for punching through bone without damaging the broadhead.
Cut-on-contact tips don't have to punch through the hide, instead they slice through it. This needs little energy, thus maximizing penetration. Cut-on-contact tips are a favorite with traditional archers and those shooting low-poundage bows
Mechanical heads aren't ideal for every situation but they do meet a need plenty of bowhunters use them with great success.
The biggest advantage of Mechanical heads is that they fly like field points and need very little tuning to get tight groups. The problem with these broadheads is that the blades are not supported on the trailing edge. Look for blades that use thicker metal they withstand greater stress and have less flex upon impact.
Also look closely at the grooves that the blades sit in, I have found many to be too thin, which causes them to clog with dirt after a pass through shot. You will need a tooth brush in your kit for field cleaning, and the very thin grooves often cant be cleaned easily in field.
Also, the length of blade you select should be limited when targeting larger species to ensure good penetration. Although I have not shot anywhere close to all the mechanical broadheads available my personal favourite for shooting and most importantly durability is the NAP Killzone. (Not the Spitfire) They have wide groove for the blades that are easily cleaned out and thick blades that I have never snapped on a bone.
Front Deploying and Rear Deploying Mechanical Broadheads
As a rough guide mechanical broadheads are available in two options, front deploying and rear deploying.
Front deploying broadheads have blades that are hinged at the rear of the broadhead, and pivot out from the front upon contact. The blades typically open up after they are inside the animal, which ensures the blades are razor-sharp when cutting through the engine room. The entry wound from front deploying broadheads are smaller than rear-deploying broadheads.
Rear-deploying broadheads have front-pivoting blades that shoot outward from the rear of the broadhead, the result is full-size entrance and exit holes. This type improves blood trails and the blades are deployed earlier.
Mechanical broadheads come with blades up to 2-3/4", but bowhunters should be wary of these for large game, try to limit the size of broadheads to 1-1/2". Smaller blade diameters give maximum penetration with bigger-boned animals.
Another consideration is the force and energy driving the pointy end. Industry experts recommend at least 55 ft.-lbs. of kinetic energy for the larger heads and 65 ft.-lbs. of kinetic energy when going after Red Deer, Wapiti and large game.
Again as a rough guide 65 ft.-lbs. of kinetic energy translates roughly into the result achieved by launching a 400- to 500-gr. hunting arrow with a 60- to 65-lb. compound bow.
Techie Stuff – Calculate your KE
You use this formula so you can calculate kinetic energy then you know exactly what you are producing with your bow set up:
ke =M * v2 / 450,240.
ke=Kinetic Energy, M=mass (weight of hunting arrow in grains), v= velocity of hunting arrow in fps, 450,240 = (gravitational constant of 32.16 * 7000 [gr.])
For example: A hunting arrow with a weight of 450 gr., traveling at 265 fps will have 70.19 ft.-lbs. of kinetic energy. (450 x 70,225 (265x265) / 450,240 = 70.187).
Tuning time is time well spent no matter what your broadhead. A good option for mechanical broadheads is to shoot the smallest diameter, ensuring maximum penetration and maintaining the advantage of the accuracy characteristics of mechanicals.
Now that you have determined which type of broadhead head you, you need to think about weight. Industry experts recommend 100-gr. heads for carbon and lightweight aluminum shafts, and for heavy aluminum shafts, 125-gr. heads. But in New Zealand if you want wind and deflection protection I feel 125 grains minimum for all medium to large game. But this will come down to your personal chioce and will depend on the GPI of your arrow, insert choice and target game.
When you have picked your weight and style of broadhead you want to use, it is paramount that you take the time to set up and tune your bow for excellent broadhead flight. Before you start tuning, you should check head alignment by spinning hunting arrows (like a spinning top) to make sure there is no wobble. Putting aside half a dozen hunting arrows strictly for hunting is great practise, and keeps these arrows free from wear during practice sessions.