Long Range Bow Tuning
They can boast to me all day long about lasers and paper tuning but there is nothing like tuning a bow at extended ranges. You can think “It looks good!” during a paper tuning session and then always seem to find a little more accuracy at the long butts. I believe that the added concentration on form and sighting when focusing at long distance is at least half of the story. If you are shooting with a partner and your arrows are numbered, have him make notes about where you think each shaft has gone (i.e. “6 o’clock and low”) otherwise known as “calling the shots”. Then, when retrieving your shafts compare the notes to the actual impacts. There will be some shots you know you blew. There will be others that you also know had perfect form and release. These are the shots and groups that count. Remove all of the known “fliers” and measure the remaining group size. Then making incremental adjustments to one’s rest and/or nock height may reveal major group differences you would never have seen on the torn paper at six yards or at the 20 or 30 yard line. If you get lost, you can always go back to the paper tear method and start over.
This process can take days if need be. It’s a long time till hunting season gets here and if everything works correctly, you will need only one shot at that buck. A tired archer makes for poor shooting. Stop before you do get tired. Where the groups actually hit is immaterial. Group sizes are what need noting. If you make an adjustment in one direction and groups get better, keep going in that direction until the groups deteriorate, then move that adjustment back to where it was best. Shoot again to confirm your original results and ONLY CHANGE ONE ADJUSTMENT AT A TIME! (I.e. right/left and then up/down on your rest or nock set) After you have found the optimum group sizes you can reasonably expect and have finished polishing your groups, you can adjust your sights to “zero”. Of course, the use of a sight bubble level and making sure the sight has been adjusted for all three axis makes long distance shooting much more accurate. Note how these days levels are showing up on more and more long distance rifles. Even a modest cant will throw impacts out of the main group.
If you are shooting five inch groups at 50 yards, that’s pretty good but a reduction of just one inch in group size translates into a significant (20% reduction) change.
I have also found that using a target spot large enough to clearly see around your sight pin is critical for obtaining repeatable groups. For instance, if you are using a .019 pin, use a bull’s eye that shows at least twice the diameter or the pin bead. The human eye will naturally center the two images if both can be clearly seen. If the spot is partially obscured by the pin, the eye has no repeatable reference with which to center.
Most of you wouldn't hesitate to experiment with the feeding of your pet rifle. Look at this as load development for your bow.
Remember, small, incremental adjustments and the taking of notes can pay huge dividends.
Have fun and watch your buds show new found respect for your skills!
“The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter can not be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles.”
Col. Jeff Cooper