November 04, 2010
By Curt Wells
Using an Easton Bow Force Mapper tool, I attempted to measure the pressure required to open rear-deploying heads like the Rage 2-Blade (top left) and Trophy Ridge Undertaker (bottom left), and over-the-top mechanicals like the NAP Spitfire XP Pro (top right), Crimson Talon Black Mamba (middle right), and Eastman Outfi-tters FirstCut Tri-Force (bottom right).
What makes the subject particularly contentious is the lack of real-world testing. No method exists -- nor will one ever -- for effective, realistic testing of broadhead performance. Even if you could line up 30 deer and shoot each one with a different broadhead, a multitude of variables would render the experiment useless.
Countless unscientific tests have been performed on broadheads from shooting them through plywood, tires, foam targets, beef rib cages, and cement blocks to high-tech ballistic gel. But until someone finds a moving, reactive target with thick fur and elastic skin wrapped around a cage of bone and filled with mushy organs and viscous lubricating fluids, results of penetration tests will remain more supposition than science.
That doesn't mean all broadhead testing is pointless. Durability tests can reveal weaknesses in structure, and basic practice will expose flight problems.
When bowhunting, good shot placement is always highest priority, and good placement is assured only when your bow is tuned, your aim is true, and your chosen broadhead flies well. Sharpness follows close behind. To do their intended work, broadheads must be scary sharp. If yours are not, either learn to sharpen them or get new ones.
Now, let's tackle the toughest question of all: How much kinetic energy does the deployment of the blades on a mechanical broadhead consume?
Using a digital scale, Easton's Bow Force Mapper, I attempted to measure only the force necessary to deploy the blades on various mechanical broadheads.
With the scale rigged to a loop at the nock end of an arrow shaft, and a ferrule-sized hole precut in cardboard, I attempted to force each broadhead through until the blades fully deployed.
Admittedly, this is a very crude experiment, valid only for comparison, and even then it's rife with problems, one of which popped up when testing so-called "over-the-top" broadheads -- those with forward-facing blades that scissor backward into the open position upon contact with an animal. Because cardboard has no give, as live fur and skin do, the blades would not deploy. Rather, the tips of the blades just penetrated the cardboard. I repeated the test using soft, tanned blue wildebeest hide with a hole in it and still could not deploy the blades with any of the over-the-top broadheads. At least not with pressure I could safely measure.
The only exception was Aftershock Archery's Hypershock head. This is a "tweener" design because it's over-the-top but designed to open after penetrating the skin. I measured the force needed to deploy the Hypershock 100's blades at 4.5 pounds.
This isn't to say over-the-top mechanical broadheads are not deadly; they are. I just haven't devised a good way to measure the energy needed to deploy the blades.
However, my test method worked very well on heads with rear-deploying blades. For example, my digital scale showed that it took 3.2 pounds of pressure to deploy the blades on a Rage 2-blade broadhead. Tru-Fire's new Switch Blade required 1.8 pounds of force, and the G5 Outdoors Tekan's blades popped open with just 1.2 pounds of pressure.
Curiously, the Trophy Ridge Undertaker required 14.5 pounds of force to open the blades, but that's deceiving. The stretching of a rubber band that captures the back edge of the three blades is what required that much force. The rubber band slides off at impact, and without it, the blades open with less than a half-pound of pressure.
While the amount of energy needed to open mechanical heads varies according to design, a more significant factor in real-world penetration is the larger cut diameters of many mechanical heads. Long, sweeping blades cut huge wound channels but also create drag, which can slow penetration.
Here's my point: If you plan to drive a three-blade head with a 13â„4-inch cutting diameter through a bull moose and expect an exit hole, you'll need serious kinetic energy, regardless of whether your broadhead's blades are fixed or mechanical.
I doubt my crude experiment and observations will settle any broadhead arguments. When bad things happen, poor shot placement is usually the culprit, but the broadhead often gets the blame.
Of course, the greatest advantage of mechanical broadheads is their low profile, which contributes to exceptional flight and precise shot placement. Throw easy-opening blades and massive cut diameters into the equation, and even diehard fixed-blade advocates are taking a second look at mechanical broadheads.
Here's a rundown of some mechanicals that have survived the broadhead wars -- and some likely to start new ones.
The Crimson Talon Black Mamba features a Spiral Kut Tip, as well as a spiral design built into the over-the-top blades, which have a 11â„16-inch cutting diameter. The Crimson Raptor is a four-blade head with a large, nasty-looking cut-on-contact fixed-blade tip. The offset mechanical blades create a total cutting diameter of 11â„2 inches. A technology called "Inertia Trigger Cam" releases the blades on im-pact so they deploy without friction.
Eastman Outfitters' FirstCut line of mechanical broadheads features varying sizes of fixed, cut-on-contact tips followed by over-the-top mechanical blades. The FirstCut ST-3 Titanium sports a lead blade 7â„16 inches wide, and the three mechanical blades open for a 11â„2-inch cut. It can be converted from 85 to 100 grains. The FirstCut EXP 100 has two blades that open to 11â„4 inches, and the three-blade Tri-Force cuts a hole 11â„2 inches wide.
The Grim Reaper Razortip is less prone to "kick-outs" thanks to the full 5â„8-inch distance from the tip to the leading edge of the blades. The tip penetrates deep enough that the cut path is established before the blades make contact and de-ploy. Tiny blades on the tip start the cutting and, once opened, the main blades follow the same path. These 100-grain broadheads cut a swath 13â„8 inches in diameter.
The Innerloc EXP is a versatile 100-grain mechanical broadhead that gives two cutting-diameter options -- 11â„8 or 17â„16 inches. By reversing the Stop Collar, you adjust how far the blades open, changing the cut diameter. A Cliploc sys-tem keeps the blades in place without rubber bands, and they snap into place, either open or closed. Blades are easily replaced, and integrated practice blades are available, as is a two-blade model.
The Spitfire XP Pro from New Archery Products is the latest version of this popular mechanical head. The Spitfire XP Pro features a replaceable cut-on-contact tip blade. It's available in 100 and 125-grain models, both with .030-inch-thick blades that cut a 11â„2-inch wound channel. The blades are Diamized for extreme sharpness. No o-rings or rubber bands are needed. This head is compatible with Easton's Hidden Insert Technology.
The WASP Jak-Hammer SST is a 100-grain, three-blade head that has been around a long time -- and for good reason. This over-the-top broadhead features an extremely sharp tip and stainless steel, .036-inch-thick blades that cut a wound channel 13â„4 inches in diameter. It's also available in a 11â„4-inch cut.
The Hypershock broadheads from Aftershock Archery are a different breed. They're actually designed to open after they've penetrated the animal's skin, thus saving kinetic energy for penetration rather than cutting hair and hide.
Two curved blades open to cutting dia-meters ranging from 13â„8 to 23â„4 inches, and they're available in 80, 100, and 125-grain models. This design is not susceptible to kick-outs on angled shots, but it does not create a large entrance hole as some designs do.
G5 Outdoors has redesigned the Tekan, a 100-grain mechanical with a large cutting tip on a one-piece ferrule. The company has reduced the cutting width of the tip to 1â„2-inch and increased the total cutting diameter from 15â„16 inches to 11â„2 inches. The leading edge of the me-chanical blade is serrated to assist deployment, the o-ring retention system has been improved, and a new all-black finish completes the facelift.
The SlipCam Rear Blade Deployment System of the Rage Broadhead has been a hot topic in broadhead discussions. The blades open completely upon impact, creating a massive entrance hole. The 2-Blade Rage is only 3â„4-inch in diameter in flight, yet expands to 2 full inches upon impact. A stainless-steel blade at the tip starts the cutting, and two .035-inch-thick blades slip backwards into position, eliminating the chance of a deflection. The o-rings have been improved and a 3-blade, 11â„2-inch cut model is available.
Trophy Ridge, now owned by Bear Archery, offers two exceptional mechanical broadheads. The Rocket Aerohead Steelhead is a long-time killer broadhead that comes in a 100-grain version with a 11â„8-inch cut or a 125-grain model with a 11â„4-inch cut. Both have three blades and a very low profile for outstanding flight.
A new broadhead called the Under-taker uses "Piston-Hammer" technology to ensure full pre-entry blade deployment. Upon impact, the piston-like ferrule drives forward, forcing all three blades into a 11â„2-inch cutting diameter. This head is very low-profile in flight -- only .55-inch in diameter -- so it flies with precision.
Better known as a release-aid company, Tru-Fire entered the broadhead market this year with the 100-grain Switch Blade. A unique Oversized Tip Technology -- OT2 -- clears the path and ensures blade deployment upon impact when the tip is driven back, causing the three blades to fly open to a 13â„8-inch cutting diameter. No o-rings or rubber bands are needed to keep this head in a very low-profile configuration.