By George Tekmitchov
FOC, or Front of Center Balance, describes the percentage of the arrow’s total weight that is located in the front half of the arrow. The more weight that is located in the front half of the arrow, the more forward is the arrow’s center-of-balance, and the more stable the arrow flight- up to a limit.
This doesn’t have to be complicated- on the Easton website, when you look at any given arrow, if you simply select the recommended point on that page to go with your shaft, you will automatically have a suitable FOC for that shaft.
Arrows with a negative FOC value (too light of a point) are inherently unstable in flight. In one specific application, this is an advantage- Arrows used for flight archery competition (sheer distance) are usually deliberately set up with a slightly negative FOC to get them to “float” at the apex of their flight trajectory, eking out a bit more distance.
However, for target archery and bowhunting, a positive balance is quite important.
Positive FOC balance, within limits, improves performance in side-wind conditions. Optimal FOC is most important for target shooters participating in longer-range shooting competitions, particularly past 50 meters.
However, “more is better” has some limits. Excessive positive FOC balance, combined with marginally excessive drag from fletching, can lead to an unpredictable “nosedive” at longer target distances, as the arrow loses momentum.
Excess FOC will also cause a given arrow to have a lower dynamic spine, which can cause problems for tuning.
Variables affecting FOC balance are the arrow shaft mass, the point/insert mass, and the mass of fletching and nock. For example, a lighter arrow shaft with a 100 grain point/insert and light weight fletching will have considerably more positive FOC balance than a heavier shaft with the same point/insert weight of 100 grains and heavier fletching.
In bowhunting applications, the actual FOC balance is already likely to be well within a usable range, due to the mass weight ranges of most broadheads and insert combinations, along with the mass of most arrow shaft options suitable for hunting.
Having a particular FOC is less relevant in most typical bowhunting situations (short-range shots), as long as the FOC has a positive value, but a somewhat higher FOC value becomes important for longer-range shots, especially when shooting lower-poundage bows.
Target archery FOC range recommendations
Generally, for target archery, an F.O.C. range of 7-15% indoors, and 10-15% outdoors, will fly with good stability, optimal momentum, and accurate trajectory from 0-90 meters.
Greatly exceeding this FOC range can cause vertical dispersion at longer distances, especially with lower overall mass arrows.
Excessive FOC (over 20%) can also make finger release consistency much more critical, as the inertia of a too-heavy point can make the arrow over-react to slight differences in finger release.
Arrows with lower FOC values (under 7-10%) will not track as well in outdoor windy conditions, but generally work well at 18M.
Bowhunting FOC Range recommendations
Easton recommends a 10-15% F.O.C. for hunting setups requiring greater momentum, and optimal accuracy – especially for longer distance shots.
Again, if you simply select a recommended point for any given model shaft, FOC takes care of itself.