To Measure Your Existing String: Hook string onto a nail, draw the string as tight as possible, and measure from end to end (including the end loops). This is your ACTUAL length.
What is AMO?
AMO length refers to the length of a bow as standardized by the Archery Manufacturers and Merchants Organization (AMO). The AMO is an industry trade organization that sets standards for archery equipment, including the measurement of bow length.
But because bows (riser and limbs) are essentially curved and the string is straight, the two are not the same length. Typically a recurve/longbow string made of more modern material such as 652 Spectra, Fast Flight, 8125, etc., will be 3″” shorter than the bow.
So for example, a 66″ recurve or longbow requires a 66″ AMO string, but the ACTUAL length of the string will be 63″ (3″ less). Similarly, a 72″ recurveor l ongbow requires a 72″ AMO string, but that means the ACTUAL length is 69″ (3″ less).
HOWEVER …
If the string is made from material which provides more stretch and elasticity, such as those made from Dacron (B50, B55, etc.) then the rule of thumb is 4″ shorter than AMO. So for example, a 66″ AMO recurve/longbow requires a 62″ Dacron string (4″ shorter) to account for the “creep” or stretch of the Dacron material.
