Bow-Tuning Shortcuts -- Part 4, Getting It Perfect
If you've been following this series you now have a bow, new or old, set up and ready to shoot. Before you can begin shooting seriously though, you need to check tuning to assure arrows are flying laser straight. First conduct a rough sight-in, starting a few yards from the target and then stepping back to 20 yards and sighting that pin solidly. Any obvious visual tuning flaws - arrow kicks, bobbles or porpoising - we'll address shortly.
You should've consulted an arrow-selection chart, plugging in variables like draw length and weight, tip weight, cam style (aggressive or mild), and release style (mechanical aid or fingers). If a spine/deflection recommendation sits at the group middle, you're golden. If sitting on the cusp between two deflection groups (or even near it), choose the stiffer option. This makes broadhead tuning easier.
Now create a 2-foot-square frame from inexpensive furring strips (1/2x1-inch). Stretch clean butcher paper across your frame and secure with staple-gun or tacks, creating a tight surface. Set before a target backstop, stand 10 feet from paper, shooting an arrow through the face. Resulting tears reveal how arrows are exiting your bow. If you've assembled your bow according to previous instructions, and selected the proper arrow-point weight, you should see clean bullet holes with accompanying fletching cuts.
Leftward tears (right-hand shooter; reverse for left-hand) indicate an arrow that's too flimsy (or too long), a rest adjusted too far from riser, or tip that's too heavy. Right tears indicate an arrow that's too stiff (or too short), a rest adjusted too close to riser, or tip that's too light. Obviously, adjusting the rest is the cheapest option, changing arrow length second (when possible), adjusting tip weight last. Sometimes you just can't tune an existing arrow, typically one too light for a high-energy cam system.
Continuing; Upward tears indicate an arrow exiting the bow tail up, thus a nocking point that's too high. A downward tear reveals just the opposite. This is a simple matter of adjusting nock locator accordingly.
Once your bow's punching clean peper holes, create a vertical line on a large target face with plumb-bob and magic marker. Paying close attention to your sight's bubble level, shoot a 3-shot group from 20 yards, adjusting sights if necessary so arrows center line. Now back to 30 yards, and using the 20-yard pin, shoot another 3-shot group. And again at 40 yards; again with 20-yard pin. A perfectly-tuned bow should group arrows on or around the vertical line. If it doesn't, make hair's-width windage adjustments to the rest until arrows group on line at all ranges, adjusting rest arm(s) toward groups. Be patient. This is a trail-and-error process.
Finally, install broadheads on two arrows, field points on two more. Repeat vetical-line test (shooting broadheads first to avoid slicing fletchings). Broadheads and field points should group simularly (an inch or two difference sometimes detected due to weight variations). If they don't repeat directions above.
Your bow's now ready for serious sight-in and shooting.
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