September 08, 2017
Faster crossbows pushed the broadhead industry to retool so that the heads could withstand 400-plus-fps velocities. Are 150-grain broadheads in our future?
Everything changes. From the weather to the latest fashions to the cars we drive, nothing stays the same. Such is the case with crossbows and the broadheads archers fit to the business end of the bolts they use. From old-school fixed blades to today's mechanicals and hybrids, broadheads designed for crossbows have advanced light years from what they were when my father was packing his Wham-O Powermaster into the field. And yes, that was quite a while ago.
But how have they changed? What course will broadhead technology take in the next decade?
"We've come a long way in the past 10 years," said Chris James of Rage and Muzzy. "You have equipment now that will shoot 3-inch groups at 100 yards.
But we're starting to see the limitations of these popular 100-grain broadheads. When crossbow-specific broadheads first came out, they were 125- and 150-grain. There were very few 100-grain broadheads available. But as technology improved, especially with vertical bows, the 100-grain broadheads became the most popular. The standard now is 100-grain heads, so there was an evolution there. But there are limitations as to how wide the cutting diameter can be with these 100-grain broadheads."
Broadhead designer Dale Perry said a crossbow's kinetic energy can be 50 to 75 percent greater compared to a vertical bow. With a crossbow, you need stronger blades, a better locking system and better pins, he said.
"It's important to maintain stable flight, and to have a broadhead that will handle that kind of kinetic energy," said Perry, of Bloodsport Archery. He predicted those factors would lead to a reversal of sorts: We're going to see the industry leaving the current standard and go to a heavier 125- or 150-grain broadhead.
FIXED TO MECHANICALS
In the late 1980s, vertical bows weren't very fast and shot at 250 or 260 feet per second. At those speeds, a large fixed broadhead would fly well. But as bows became faster, it became a challenge to get the broadhead to fly right. Crossbows, then, took that another step with their 380-plus-fps speeds.
"The challenge with fixed blades was how to get them to fly properly out of a crossbow," said James. "Back in 2001, we were using 125-grain Muzzy broadheads on a 220-fps crossbow, and they worked just fine. Now you take that same head and put it on a 400-fps crossbow, and there's not enough spin to the vanes, nothing to make that bolt spiral and stabilize." With speed, arrows became even harder to control, said Perry.
With modern mechanicals, something like the Grave Digger, which Perry designed, the kick-out blades are strong, sharp and thin: 32/1,000 of an inch thick. They cut the wind, and that front-edge design makes the broadhead fly differently despite the high speeds and energy of modern crossbows.
James said there is a clearcut line between what is and what is not a good mechanical crossbow head. "The diameter of the ferrule on a true crossbow broadhead is the same diameter as the bolt itself. Crossbows, then, have their own separate components. The broadhead fits flush, which helps aerodynamically, as well as centering all the energy on the broadhead. This centering in turn helps with blade deployment."
With a vertical bow, you can simply use helical vanes to impart that spin. "But with a crossbow, we had to make shorter broadheads and put an offset to them. This way, you have a spin both front and back to stabilize the bolt."
Where's it all headed, this design and development?
"Arrow development is incremental," said Perry. "Chances are you're going to see three-year leaps in technology, but I believe you'll hit a ceiling. The materials that are available won't handle the stress."
When he designed the Grave Digger, people had said it couldn't be done. The design was there, but the machines to build them weren't.
"Design is one thing, but can you build a product inexpensively enough that people will buy it?" he said.
James said the future isn't clear, but he foresees companies pushing the limits.
"The next speed barrier is 450 fps. Then there's 500," said James. "That's three to five years, but they'll chip away at it. The problem is that the equipment — the bolts to handle the stress and the broadheads — has to come with it."
Mechanicals' Major Challenge
Mechanical, a.k.a. expandable, broadheads work on the premise that the cutting blades remain retracted during flight until such a time as the broadhead physically strikes the target. Blunt force trauma, it might be called. Or the instantaneous cessation of kinetic energy.
The concept works incredibly well; however, it does have its challenges — namely, how do manufacturers prevent the early, or premature, deployment of the cutting blades as a result of the tremendous kinetic energy created at the instant a crossbow cable is released, i.e. when the bow is fired? The solution has been a work-in-progress, with great strides in this progress and improvements being made annually.
"This early deployment was a critical consideration in the design of our broadheads," said Pliny Gale, product marketing manager for TruGlo Archery.
"The pivot point of our blades is located in front of the major area, meaning there is a natural aerodynamic tendency to hold the broadhead closed until a greater mass physically pushes on the actuating lever. A set screw and an internal friction washer also exert tension on the blades to hold them in place during arrow flight. This translates into great aerodynamic stability in flight, plus near-instant deployment as the broadhead strikes a target."
Dale Perry with Plano Synergy and Bloodsport Archery explains their engineers use advanced technology to test each conceptual broadhead design. "We use high-speed cameras," Perry said, "and painstakingly test our broadheads for flight at (the) shot, as well as at long-range distances. From this, we can get real-world data; however, ultimately putting broadheads through animals is the only way to see (all) of the variables that can happen in the field."Continual testing seems to be a common denominator in the industry, as evidenced by FeraDyne's Chris James' comments. "FeraDyne is constantly exploring and testing new materials and deployment methods. Simply by changing a substrate, you can greatly change the effectiveness of a design.
"Our new High Energy Shock Collar on all Rage crossbow broadheads has been tested to well over the speeds of today's bows using an air cannon (capable of) shooting them over 600 fps without pre-deployment, while at the same time ensuring the broadheads deploy on-target as intended.
"At Muzzy, our Hybrid is designed so it's impossible for it to open prior to impact. Here, the launch energy forces the blades to remain in the closed position as opposed to the same energy trying to 'open' them," he said.