Blazing Bolts: How Much Speed Do You Need for a Crossbow?
Just how much speed do you really need to create the best crossbow for deer hunting success? It may not be as much as you think.
Selecting the right arrow for your crossbow can seem daunting, but it isn’t rocket science. Speed isn’t the only thing to consider for achieving peak performance.
Trajectory, retained energy and noise are also factors, particularly when targeting skittish, heavy or dangerous game. Speed might not even be the most important factor. While speed-demon fans might disagree, in most crossbow hunting situations at recommended maximum range, whether Arrow A smacks into a target a fraction of a second faster than Arrow B makes little difference.
Don’t get me wrong: Arrow speed is good. Most archers understand as arrow mass increases arrow speed decreases. The opposite is also true. As arrow mass decreases, arrow speed increases. In other words, the lighter the arrow the flatter the trajectory and the faster it travels to the target.
So, faster arrows are better, right? Not necessarily. For target plinking, you bet, but for hunting game — not always. For one thing, depending upon the bow, lighter arrows might be noisier to shoot. The difference might be subtle or quite noticeable, and while it’s not overly critical when shooting targets, it is in a hunting situation.
Because there is less resistance, strings and cables move faster with light arrows, and that noise travels faster than an arrow, which means that deer, elk, wild hogs or bears have more time to react before the arrow arrives.
While a faster arrow might compensate for the louder release, it’s important to keep something else in mind: Speed alone doesn’t kill. A feather traveling at 20 mph might sting, or might not even be felt, depending upon how it strikes. But a bowling ball moving at the same speed is a whole different matter. The same is true of a crossbow arrow.
Speed is good, but whether shooting carbon arrows such as Beman’s ICS Crossbow Hunter or Easton’s Bloodline, XX75 aluminum or its carbon/aluminum Full Metal Jacket, you need retained weight, mass behind it to drive broadheads through skin, muscle and tissue into the vitals. Keep in mind, retained energy depends on two things, mass of an object and how fast it is traveling. One without the other doesn’t work.
HOW MUCH ENERGY IS ENOUGH?
But how much energy is needed to ethically put an animal on the ground?
Ah, the big question. From a hunting perspective not much really, but it depends on the size of the game and, of course, shot placement. For deer-size game, 40 pounds is plenty. If a 180-pound-draw bow pushes a 370-grain arrow at over 300 fps and whitetails are the primary target it is delivering nearly double the energy required to get the job done, enough in fact to dispatch North America’s biggest game, or the biggest game anywhere, providing the shot is properly placed. But if a lower draw-weight bow shoots the same 370-grain arrow at a lower speed, say 225 fps, it might be enough for whitetails, depending upon the conditions, but lacking on bigger game.
Keep in mind, a few feet per second with a light or heavy arrow on a particular bow makes all the difference in the world in terms of retained energy, penetration and accuracy.
Fortunately, manufacturers make arrow selection relatively easy. Most crossbows are purchased as a package complete with arrows based on that bow’s draw weight and power stroke. When the time comes for replacements you have a good idea of what to buy, or at least where to start. Regardless of material, as long as you purchase arrows of the same length and weight you should be good to go with similar results. If not, owner manuals and most manufacturers can certainly make recommendations, and it is always best to adhere to their specifications.
The arrows in most packages are usually of minimum length and weight for that particular model, and while today’s modern bows can shoot longer and heavier arrows with excellent accuracy after some sight adjustments, using shorter and lighter arrows might damage the bow and shooter at a maximum or affect accuracy at a minimum.
CARBON, ALUMINUM OR BOTH
Other factors should also be considered. Material — carbon, aluminum or a mix — straightness, diameter, spine and weight consistency, nock type, durability and, last but not always least, cost — although it should be kept in mind that you get what you pay for.
Some crossbow hunters prefer carbon shafts, others aluminum and others a mix of the two for various reasons. With today’s modern materials and high standard manufacturing practices, brands such as Beman and Easton are excellent choices, each providing what is needed for today’s crossbows.
Beman is an industry leader in carbon arrows and its popular 20-inch and 22-inch ICS Crossbow Hunter is made of durable high-strength C2 carbon with a 22/64-inch outside diameter, which is pretty much standard for crossbow arrows. The ICS Crossbow Hunter has plenty of durability and spine for high-speed bows and is fletched with enough spin to accurately guide heavy 125-grain broadheads.
Most important, straightness tolerances of +/- .003 inches and arrow-to-arrow weight consistency of +/- 2 grains assures accuracy. Easton offers a mix of 20-inch and 22-inch crossbow arrows, made from carbon, aluminum and carbon/aluminum mix, with their Bloodline, XX75 Magnum, Bowfire Bolt, Full Metal Jacket and Flatline Crossbow lineup. Each comes with a guaranteed straightness of +/- .003 inches that surpasses industry standards, uniform spines and strict weight tolerances between shafts for consistent performance.
Finally, keep in mind that properly indexing the arrow into the string latch is important. Depending upon the brand, manufacturers usually recommend half-moon or flat nocks. While most modern crossbows will shoot both, it is important to use what is recommended for accuracy, peak performance and safety. Fortunately, both Beman and Easton and other arrow makers offer their crossbow arrows with both options.
DID YOU KNOW?
Calculating arrow energy is not difficult. You will first need the weight of the arrow in grains with arrowhead installed and arrow speed in feet per second (fps). A chronograph can be used to measure speed or can be obtained from the manufacturer. Once these figures are known, multi- ply velocity X velocity X total arrow weight in grains, and then divide that figure by 450,340 to obtain kinetic energy in foot-pounds.
The weight of crossbow arrows is designated in grains. Manufacturers might provide total weight, for example 300 or 400 grains, or offer the GPI, or Grains Per Inch. If the later, you can calculate the total weight by multiplying the arrow length by its GPI. In other words, if the arrow is rated at 11.5 GPI and is 22 inches long, the total weight of the shaft is 11.5 X 22=253 grains.
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July 3, 2017 at 09:34PM