Three factors–peak draw weight, let-off percentage, and arrow weight–determine overall arrow speed.
Obviously the more draw weight a bow generates the faster the arrow will fly, and conversely the heavier an arrow becomes the slower it is likely to travel. Most hunters understand these basics of physics, but few know that the percentage of let-off also dramatically influences arrow speed.
Let-off, or the amount of weight felt at full draw, affects arrow speed. The lower the let-off percentage, the more arrow speed generated. That’s why the fastest AMO speed ratings belong to bows equipped with a modest 50 or 60 percent let-off.
A compromise of let-off percentages suits most hunters best. Low let-off bows generate blazing arrow speeds, but higher let-off bows are easier for the average hunter to hold steady and shoot accurately. Bows equipped with 65, 70, 75, or 80 percent let-off provide a satisfactory combination of speed and accuracy.
The hunter who plans to hunt at the extremes of the sport (long-range targets or large animals) may opt for the maximum speed and penetration provided with bows offering a 50 or 60 percent let-off. Those who treestand hunt for deer, black bear, and other 14- to 40-yard targets will find 65-80 percent let-off bows an excellent value.
A simple device known as an overdraw can add 20-30 fps of arrow speed to the bow you’re currently shooting. An overdraw attaches to the sight window of the bow and allows the hunter to come to full draw with an arrow that’s several inches shorter than his or her normal draw length.
Because overdraws allow hunters to shoot a shorter and lighter arrow, they can enjoy a substantial increase in arrow speed. Overdraws can be mounted on most bows that feature a cutout sight window that allows for broadhead clearance.
Round-wheel and energy-wheel bows are ideal for use with overdraws. Cam bows may also be equipped with overdraws. Unfortunately the aggressive action of the cam combined with a shorter and stiffer arrow makes it more difficult to tune the bow for consistent accuracy and to keep such a bow in tune.
Arrow rests–including the popular Timberdoodle, Superdoodle, Golden Key 3-D Golden Premier, Cavalier Equipment Predator II, and Cobra Trail Blazer–can be rigged as useful mini-overdraws. If the goal is to trim only an inch or two from the overall arrow length, these unique rests are a simple and effective way to pick up a few extra feet per second.
Performance bows have come along way in the last few years and so have hunting arrows. For years the Easton XX75 was considered by many to be the standard in the industry. It wasn’t until high-tech aluminum alloy arrows, carbon shafts, and aluminum/carbon composites appeared on the scene that performance took on a new meaning.
The Easton XX78 SuperSlam series arrows are made from super light and strong 7178 aluminum alloy that offers an incredible +/-.0015-inch straightness factor. Stronger, straighter, and lighter than the XX75 shaft, the XX78 is available in a wide variety of spines to suit all hunting conditions.
Carbon arrows such as the Beman Hunter hold all the Olympic records for target shooting and are rapidly becoming a factor among serious hunters. Beman was recently purchased by Easton and rumor has it that a totally new generation of graphite arrows may result from this marriage.
Graphite arrows are on the average five times stiffer than comparable aluminum shafts. The stiffness of graphite arrows makes them the leaders in penetration.
When an aluminum arrow strikes a target, the shaft flexes and some of the kinetic energy is directed away from the arrow point or broadhead. Graphite shafts flex very little compared to aluminum, and they deliver their complete load of kinetic energy at the broadhead. Not surprisingly, graphite arrows are becoming the choice of hunters who seek large or dangerous game.
Aluminum-carbon-competition shafts (or ACC) are an unique blend of carbon and aluminum. ACC shafts are made by wrapping an aluminum core with graphite fibers. The result is an arrow that offers the benefits of both aluminum and carbon.
ACC shafts accept glue-in-style graphite or aluminum inserts and feature an uni-bushing and adjustable nock that makes it simple to achieve perfect vane clearance. The carbon-wrapped aluminum core makes these arrows much stiffer than comparable aluminum arrows. As a result ACC shafts are fast, accurate, and they deliver better penetration than aluminum arrows.
More expensive than XX78 or high grade carbon arrows, the ACC shaft makes an outstanding hunting shaft for those who are willing to pay a little extra for performance.
A number of accessory items can help speed-bow users get the most from their bows. It’s strongly suggested that speed bows be matched with a mechanical release aid. Finger shooters will find that it’s tough to accurately shoot a bow equipped with cams. A mechanical release provides the crisp and consistent string release needed to make speed bows shine on the target range and in the field.
Simply adding a bushing-style or Teflon-coated speed slide to the cable guard can add five fps to arrow speed. Hunters should note that ball bearing model cable slides are not recommended for use on bows with Teflon-coated cable guards.
Another simple device known as a Turbo Button will add five to seven fps of speed to cam bows. Produced by Mountaineer Archery the Turbo Buttons are simply a rubber tube that’s attached to the bow string near the cams. Designed to reduce string oscillation, the Turbo Buttons are tied into place on the string and adjusted by sliding them 1/8 inch at a time and taking test shots until the best possible speed is recorded on the chronograph.
Aluminum-arrow shooters can pick up 5-10 fps of arrow speed by switching from aluminum to graphite inserts. Depending on arrow size, graphite inserts can be as much as 20-30 grains lighter than comparable aluminum inserts.
When installing graphite inserts in aluminum arrows, they must be glued in place with a quality epoxy. Hot melt and other adhesives are a poor choice for mounting graphite inserts.
Hunters may also consider using a fast flight serving material in place of traditional crimp-on string nocks. Metal string nocks rob a bow of speed and wear out the serving more quickly than a few carefully positioned wraps of serving material.
The vanes used on hunting arrows can also influence speed. Most hunting arrows are equipped with three five-inch plastic vanes. Using a shorter or cutout vane style such as Bohning’s four-inch Low Profile or Bi-Delta can add two to five fps to arrow speed. Avoid arrows fletched with four vanes. The extra vane adds weight and air drag that needlessly slows down the arrow.
Individually each of these suggestions amounts to a drop in the bucket, but collectively a hunter can add a precious 20-30 fps to his favorite hunting bow. A little speed goes a long way. On the target range just an additional 10 fps will show up in a noticeably flatter trajectory and improved accuracy. Add 20 or 30 fps, and a hunting bow becomes a whole new animal.