Technical Stuff: Bolt Testing

Put a number on each of your bolts. The archery suppliers will have decals, or write the number on the vanes. If you have more than 12 bolts use a letter decal as well to identify each set of 12, or simply keep on with the sequence on the vanes. If you use decals place them on the bolt on the side opposite the cock vane. Always place the bolt in the track that way up. THIS IS IMPORTANT. You must always place the same vane, the cock vane, in the track. If you place a different vane into the track the bolt will shoot differently. Then you need to bench test your bolts – or as close as you can get.

Use a camera tripod to give added support to the bow under the prod block. Adjust it so that you are as close as possible to your normal shooting stance at the longest distance you shoot. Try for calm weather, or at least a period when the breeze is light and coming from a constant direction.

Take a few sighting shots set your sight and then leave it alone.

Shoot your bolts in a known sequence and record where each one goes. You need to do this at least three times for each bolt. Do not change your sight setting. This way you can identify which bolts group together, and where. You will also find out which ones are totally erratic. It is not uncommon to find that some bolts which otherwise appear to be identical and straight will not group with their peers.

Here are pictures of four ends of bolts.

The first thing to note is that 6 lines have been drawn onto the face to give the “hours” to aid with describing bolt position: e.g. 9 at 9 o’clock etc.

Picture 1 includes sighter shots.

You should already be able to see that there is a tendency for bolts to group in the 9 o’clock 8/9 area or 6 to 7 o’clock in the 9. So you should understand what we are talking about.

Pictures 1 & 3 are showing the same bolts – remember the sighter shots. Picture 2 shows another set of bolts. In Picture 4 the bolts are as for Picture 2, but the number reduced to prevent damage.

The best way to record these is for one person to shoot and a second to spot, watching as each bolt goes in, and record each shot. You can then swap over using a second face. Spotting for your own bolts becomes a problem after 4 or 5 shots – trying to remember which one is which. You can walk up and record at the target, but this is tedious as the spin of the bolt usually means that it is difficult to read the numbers.

RECORDING BOLTS

Here are two ways that you can record the bolt values and position.

Use small diagrams showing the rings 10 out to 7. An example is shown in Appendix 1. On the sheet shown there are four diagrams, arranged vertically, for each bolt. Record one shot on each diagram.

The other option is to use a numeric system. Assume that a cutter is the whole score. Then clean just inside the line is score + 0.25, half way on the ring is +0.5 and so on.

Starting at 7 this gives values of 7, 7.25, 7.5, 7.75, 8, 8.25, 8.5, 8.75, 9, 9.25, 9.5, 9.75, 10, 10.25, and 10.5. Anything inside the archery “X” ring counts as 11.

Do the same thing for the hours of the clock. Realistically you will only use the hour or half hour once you get to a value of 10. Inside the “X” ring time may not exist – that’s up to you.

Which system you use depends on what best suits you, both from the point of view of making the record and for analysis.

ANALYSIS OF BENCH TESTING

Here is an example of the same record made using the two systems of recording. It is simplified as it has been created to demonstrate the point, and it is only for 12 bolts.

Bolt 10 is obviously not consistent in the result it gives, so we will discount this bolt.

The fourth shot for bolt 4 is significantly different to the other three. Something happened to throw this shot off. Discount this shot and check the bolt for damage.

Bench Testing Analysis
Bench Testing Analysis Table 1

The next table shows all the shots listed and sorted by the angle at which they struck the target.

The green acceptance zone has been set for an angle of one hour. That is a very narrow angle, considering that the proximity to the centre of the target and the shooting distance. Taking into account the score values we are looking at an area 60 mm wide by about 20 – 25 mm tall.

This suggests that bolts 6, 9, and 12 do not group with the others. Bolt 7 could be used as a back-up, but it will shoot slightly low and left.

Bolts 1, 2, 3, 4, 5, 7, 8, & 11 make a set of eight. Make your own selection from these, but bolt 4 looks like it should only be used as a reserve. On this basis 1, 2, 3, 5, 8, &11 are the set to use. Bolts 4 and 7 would be used if there are problems.

If you open the acceptance angle then 6 comes into the group, which covers two rings of the target. 7 still looks like back up only. You can take it on from there.

Bench Testing Analysis Table 2

When you do this for real you need to end up with 6 to 8 bolts, to allow for damage, that you would be happy to shoot at a competition. For a two day competition you need more bolts.

Ideally you should do this for every shoot, because shooting has an effect on bolts. You may not be able to do this, but it does need to be done reasonably frequently.

Just as for strings, bolts can become “tired” with age.

Know your bolts. Remember that testing is not the end of the exercise. Be prepared to recognise that a bolt is not performing in competition as you expect and replace it.

You will find that there are some bolts that you never take to competition, or even use for practice.

Have separate sets for indoors and out.

You should have as many bolts as you can afford, within reason. I suggest two dozen as a good compromise, but more would be better.

Every two years I make 72 bolts for my wife to shoot. These will quickly be reduced to 20 to 30 to be used outdoors, and 20 to be used indoors. That leaves about 22 that may never be used in anger, but will go into the set for routine testing. There may also be 4 or 5 that are simply discarded.

The whole point of the bench test process and its’ repetition is to find out how your bolts perform. Straightening a bolt at a competition changes its’ shape from what it was for bench testing and you will not get the result that you expected. Trust your bench testing, even if the bolt is not straight. If a bolt is not performing as you expect put it aside for now and use an alternate.

APPENDIX

Here is a blank copy of the bolt record sheet used above. It shows the target rings 10 out to 7. If you cannot put a group in this area using additional support for the bow there is something drastically wrong, and you should talk to your coach.