Preseason Broadhead Tuning – by Patrick Meitin
Preseason Broadhead Tuning – It is generally accepted that broadheads will impact differently than field points when shot from the same bow, especially fixed-blade heads. In general, this is true, as arrows flex dramatically during launch, going from zero to 330-plus fps in the blink of an eye and pulling G-forces well beyond anything modern automobiles, aircraft or even rockets are capable of. This arrow flex, or paradox, means any exposed broadhead surfaces, even the small deployment spurs of mechanical designs, in addition to various length ferrules, will interact with passing atmosphere differently than a compact and extremely streamlined steel field point. The faster the arrow, the more dramatic this effect.
That said, a perfectly tuned compound (or precisely balanced traditional arrow) can minimize these discrepancies so that they fall well within the standard deviations introduced by a launch platform held by living, breathing humans. In other words, if everything is in perfect harmony, your 4-inch field point groups might become similar or slightly larger 4 ½- or 5-inch broadhead groups. This is my goal from the beginning while setting up a hunting bow.
Many believe paper tuning is the final word while setting up an attached arrow rest to a compound bow. To my mind paper tuning is only a good start. After achieving a perfect bullet hole through paper, I then conduct what I call walk-back tuning. This requires a fairly tall, vertical target or safe backstop. Create a conspicuous aiming point high on the shooting face, and then use a plumbline or carpenter’s lever to ink a vertical line below the aiming spot and down the target face.
Start by shooting at your spot from 20 yards and work to ensure your pins are perfectly centered. Now back to 30 yards, aiming at the same spot with your same 20-yard pin. Arrows will obviously impact lower. Continue at 40, 50, 60 yards, placing the 20-yard pin on the original spot each time, backing up until arrow groups become inconclusive. The goal is to assemble groups along the center line. Yet you may notice groups wandering left or right as you back away from the target, signaling your rest is very slightly out of center shot.
Preseason Broadhead Tuning – To remedy this make micro adjustments to your arrow rest—we’re talking one or two clicks on a micro-adjust system, not big movements—moving the launcher/arrow towards center. When all arrow groups at all ranges center up, that bow is super tuned and should group field points and broadheads of all styles more closely together.
While tuning a traditional bow bare shaft tuning is the best way to find the sweet spot, shooting a fletch-less arrows at about 15 yards while adjusting the nocking point up and down, brace height higher or lower, and in some cases, even striker-plate thickness while shooting off the shelf. Juggling point weight by adding 5-grain brass washers (Precision Designed Products, a.k.a. PDP) can also help here.
That said, a particular broadhead brand or style may still impact differently enough to make a difference in the field. You might first consider changing to a more substantial fletching size or adding more helical to those fletchings to provide more positive steerage—using a 4-inch vane instead of a 2-inch, or four 2-inch instead of only three, for example. This is made easier via today’s drop-away arrow rests…
Boosting F.O.C. might also do the trick, bumping it to 12 percent (or higher) instead of the minimal 10 by switching to a heavier insert (steel or brass, for instance) or adding steel insert weights (PDP).
Preseason Broadhead Tuning – Determine F.O.C. through these steps:
- Measure arrow length from the nock throat to shaft cut-off point. (We’ll use 28.5 inches as an example).
- Divide that number by two, or multiply by 0.5. (28.5/2 = 14.25 or 28.5 x 0.5 = 14.25).
- Find the arrow’s balance point and measure from nock throat to this point. (let’s say 19.0 inches).
- Subtract half the total length from the balance point number. (19.0 inches, 14.25 inches = 4.75 inches).
- Multiply that number by 100. (4.75 x 100 = 475)
- Divide resulting number by total arrow length. (475/28.5 = 16.6 percent F.O.C.).
If after going though these steps you still find your broadheads impact considerably different from field points—and you are still determined to use that broadhead—you have no choice but to resight your bow and shoot only broadheads during practice, granted you are receiving perfectly clean arrow flight. If you are detecting the smallest amount of rear-end kick or porpoising, choose a different broadhead, as these symptoms will only be accentuated by field conditions such as wind or light deflections.
The real point here is you will not know for sure that your field-point/broadhead impact is different if you do not thoroughly audition both. I am shocked to see how many bowhunters don’t go through the necessary step of shooting—even minimally—their broadheads before heading afield. This is utterly irresponsible, as a worst case would include a broadhead tipped arrow that veers into the guts of a big game animal and causing unneeded suffering following an otherwise well executed shot. I know broadheads are expensive, but responsible bowhunting requires sacrificing at least one head for preseason shooting—just to be certain and confident arrows will go where they are directed.
Preseason Broadhead Tuning – Shooting broadheads requires a target made from solid molded foam like Morrell’s High Roller, BIGshot’s Titan, or Rinehart’s Eighteen to One, as examples, or fused layered foam like those from BLOCK to avoid undue damage. Bag targets should never be shot with broadheads as it will cause permanent and irreparable damage, while broadheads can also be hard on banded layered foam. With a bowhunting season looming, I generally shoot nothing but broadheads for a week prior to opening morning.
The only caution after target practice is complete is to set those broadheads aside for practice only, or install fresh blades to ensure maximum hemorrhaging when you begin bowhunting. Better yet, some mechanical designs include effective blade locks that ensure interior blade edges are not engaged and remain razor sharp.
Learn more about tuning here