To calculate Forward of Center (FoC) arrow balance for a particular arrow set-up (mounted with head/broadhead of choice):
- Measure overall shaft length from bottom of nock to back of head, for example 30″
- Divide that length in half (15″) and mark the shaft’s linear center at that point
- Balance the shaft on the edge of a ruler or other thin support and mark that spot
- Measure the distance from linear center mark to balance point mark, for example 5.5″
- On the chart, plot overall shaft length (30″) along the top, horizontal column
- Plot FoC measurement (5.5″) on the left, vertical column
- Where these two columns meet in the chart is percentage FoC for that arrow set-up, in this example 18.33%
Up to 12% is standard FoC; 13% to 19% is high FoC; while 20% and above is extreme and what we’re wanting in a big game arrow system. Generally, the higher the FoC, so long as arrow flight remains perfect, the greater the penetration potential.
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