For the majority of recurve archers 'how to pressure button tune' becomes a choice between a walk back approach or a bareshaft approach. The following is brief discussion of The pluses and minuses of the two methods.
For pressure button tuning to be a painless experience I believe two requirements are needed.
The first point is fairly obvious but in practice I think causes a lot of problems. You often see advice about changing pile weight, brace height nock point weight etc. in order to turn a bad arrow selection into a tuneable arrow, but this is usually suggesting rearranging the deck chairs on the Titanic. Only real way of turning the wrong arrow into a tuneable arrow is to change arrow length or draw weight, only in rare cases a practicable option.
Re point 2, although there are many 'how to tune' guides around you get the impression that many of them were written by people who had little or no understanding of what tuning is actually about. As a result there are lot of 'alchemical recipes' around which are either over complex, ambiguous or just plain nonsense. You get a series of steps which for an individual seems overall to work but no recognition that step 14 which involves locking up a pressure button with a matchstick or standing on one leg with a bag over your head serves no useful purpose and isn't actually necessary.
Fundamentally tuning is about getting a bow-arrow-archer combination that produces the minimum arrow spread i.e. group size at a specific target distance and in a specfic working environment (wind, temperature). This is a time consuming process and requires a high level of archer skill. For the majority of archers what they call tuning is establishing that they have the correct bow-arrow match and have a reasonable bow set up for their skill level.
All tuning methods are mainly used to adjust the amount and direction of rotation the arrow has at launch. With the walk back method this is done by directly determining whether the arrow travels in a straight line or not in the vertical plane from launch to target. With the bareshaft approach you estimate both the amount of arrow rotation (gap between fletched and bare shaft) and direction of arrow rotation (bare shaft left or right of fletched shaft). When choosing between the two methods the criteria has to be which method is the most suitable for the archer's skill level. The walk back method is method that can be used by any level of archer. The positive result it gives you is that there is no or minimal need to adjust the sight pin windage when changes distances during a tournament. The 30m bare shaft approach requires a higher skill level and should really be regarded as the first step on a group tuning process. There is not really any evidence that on a practical level for the average archer, if both are done correctly, a bareshaft approach will produce better results than a walk back approach in terms of score.
The sensitivity of a button tuning method is going to depend on the properties of the arrow (weight, fletching size etc.). In the following example I'm assuming a 'typical' target arrow, a 29" ACE-570. The bow is fairly poorly tuned. In practice whether using a walk back or bareshaft method a number of arrows will be shot and the centre of the group determined. The group centre is assumed to be the point where the perfectly shot arrow would hit so it depends solely on the bow setup not on the archer. Of course how accurately you can determine the centre of the group does depend on the skill of the archer, so there is always some limitation on how accurately you can tune.
The following two graphs compare the sensitivity of the walk back and bareshaft approaches at 30 metres and 70 metres for the same (mistuned setup) tuning situation. The blue line represents the flight path of the perfectly shot fletched arrow and the red line the flight path of the corresponding perfectly shot bareshaft arrow. The horizontal axis is the distance and the vertical axis the horizontal displacement of the arrow.
The first obvious point you can see from the 30 metre graph is that trying to bareshaft tune this
arrow at around 20 metres would be a complete waste of time as the bareshaft and fletched arrows would
be in the same group almost irrespective of the tuning. All that will happen as you change things is that the
bare/fletched arrow group will move around the target face.
With a walk back approach the distance the fletched arrow is from centre at 30 metres is around 9cm to the left. This distance is probably identifiable with an average archer's group size.
With a bareshaft approach the bareshaft is hitting about 4cm to the left of the fletched arrow, maybe just about identifiable by the average archer.
Clearly for these arrows at 30 metres the walk back approach is going to be easier to do for an archer of lower skill. However the accuracy of a walk back at 30 meters is going to be low. As discussed elsewhere the bareshaft method should be done at around 30m distance and the overall tuning results (button spring and nock point combined) from doing a bare shaft at shorter or longer distances is going to be less accurate.
At 70 metres distance with a walk back approach the fletched arrow hits about 18 cms to the left of
centre. With a bareshaft approach The bareshaft arrow hits around 17 cms left of the fletched arrow. So
the two approaches in terms of group centres have about the same sensitivity. As mentioned above the normal bare shaft method should be done
at around 30 meters for best results. Shooting bare shafts at 70 meters is normally used to reference a group tune as for a tuned system the bare
and fletched arrows do not group together at 70m. With the walk back method the longer the distance you can identify the group centres at
(as in are the arrows going left or right) and move that group centre to the target center the better the result.
Point to bear in mind is that the group sizes at 70 metres will be larger than the group sizes at 30 metres and that the bareshaft groups will be proportionally larger than the fletched arrow groups. For the average archer grouping fletched arrows at 70 metres is not (much) of a problem. To group bareshaft arrows at 70 metres you have to be pretty good.
It is perfectly feasible for an archer, at shorter distances, to use both walk back and bareshaft methods at the same time, just shoot a bunch of both bareshaft and fletched arrows using the controlled bow alignment you need for a walk back. You get both the fletched and bareshaft group centre positions at the same time so you can use the two apporaches to verify each other. Going to longer distances you just drop the bareshaft at around 50 meters where the physical differences of the bare shaft start to distort the result.
On a practical level although the above suggests a walk back approach to be the easier method requiring less skill it is a technically a more difficult tuning method. The bare shaft method is technically simple, quick and if you can move the bareshaft across the fletched arrow using spring adjustment only gives an unambiguous result. A lot of things can go wrong with a walk back approach. Because it requires shooting arrows at a distance, say 70/90 metres, any errors resulting from an incorrect sight windage, misaligned sight bar, variable head position, bow canting or anchor point and the archers own arrow spread at distance make the results uncertain.
Always bear in mind that a basic tuning approach will only result in a reasonable setup, quite a long way in absolute terms from perfection though for 90% of archers perfectly adequate for their level of skill.
Last Revision 18 February 2015