AMO standards are similar to spine charts in that they' re a good starting point and rule of thumb but that' s about it.

There are so many variables that it' s impossible to make a " standard" unless all the bows are of the same design geometry and length. 66 inch recurve bows typically will have a brace height of 8.25 to 8.75 inches for best performance. 68 inch recurves 8.75 to 9.25 and 70 inch 9.25 to 9.75.

Additionally, since AMO is measured along the limb and not from end to end, the curve of the bow will affect the " length" . This isn' t such a problematic deviation with longbows because they' re more or less straight. As a rule of thumb, the longer the recurve, the more it will lean toward 4 inches. The shorter, the more it will lean toward 3. Longbows are typically close to 3 inches.

Now if we' re talking B-50.... allow about an inch and a half for stretch on a 60" bow if you' re building the string yourself. And for those who don' t know how to stretch their own B50 strings, just string the bow and put it on your lap belly up (string toward you - handle on your lap). Then press down very firmly on both limbs. The limbs will act as levers on fulcrum (the riser) and provide you the mechanical advantage necessary to stretch that string properly. You can shoot 200 arrows out of a bow and still not take all the stretch out of a B-50 string, but once you do take it out, it becomes very stable. " shooting out the stretch" just doesn' t work.