Knowing what draw length a bow is set to is important so that the archer can properly select and setup their equipment. Most people rely on what setting the bow is set at to determine the draw length of the bow. Unfortunately this is not always accurate as many bows are actually set anywhere from correctly to 3/4″ or more higher than their rating. Thus buying a bow with a 28″ rating may actually get you one that is set to 28 3/8″. Often bows come this way from the manufacturer, other times the strings may have stretched or the bow may not be tuned properly and the draw length is off. It is in the archer’s best interest to measure their own bow rather than rely on the setting or markings of the bow. It is also a good thing to check periodically to make sure that nothing has changed on the bow.
AMO Draw Length
The AMO draw length is what manufacturers use to rate their bows and is the draw length that is printed in the bow’s specs. Unfortunately the way that the AMO length is measured can be a bit confusing because it is not an exact measurement. AMO draw length is calculated by taking the actual draw length and adding 1 3/4″.
Checking a Bow’s Draw Length
There are several methods that can be used to measure the draw length of a bow; some more complicated than others. Many pro shops and even home shops use a draw board or similar device. Another way is to have someone measure the draw length while you are at full draw although this can be awkward and somewhat dangerous. The simplest and easiest way that I have seen and the one that I use when my draw board is not available, is to make a draw arrow.
Before a draw arrow can be useful, you must know what exactly you are measuring. The draw length of the bow is determined by measuring from the nock point to the point directly above the deepest part of the grip, where the arrow crosses the riser. This point is easily found with the use of a bow square.
Attach the bow square to the bow string across from the grip and measure the deepest part of the grip. Make note of this measurement.
Now move the bow square up to the rest. Make a mark on the riser at the previous measurement. I prefer to use a small strip of painter’s tape so as not to make anything permanent on the riser.
Next you will need an arrow that you can make draw length markings on. Using a tape measure or similar, place the end 1 3/4″ past the throat of the nock (remember that AMO is actual draw length plus 1 3/4″.) Mark the arrow at whatever increments you would like; I am using 1/4″ on my arrow.
Nock the marked arrow, draw the bow back and have someone look to see where the mark on the riser matches up to the measurements on the arrow.
This simple method is easy to use and very reliable.
Other posts you may enjoy:
- Archery Tips 5 – Estimating Draw Length
- How to: Estimate Bow/Arrow Speed
- How to Measure Arrow Shaft Specifications
- 2013 Alpine Archery – Roxstar and Verdict
- TAP (The Archery Program) Archery Software