RE: Percentage of FOC
I think speed has an impact on accuracy with FOC also. Last week I was shooting my .300 spine 100 grain tip arrows at around 260-265 fps with a 6.5% FOC. I ended up getting 3 inch groups at 60 yards with my hunting arrows (70# bow backed down half way). Went back out with 70# bow maxed out after getting correct pivots installed and my bow was now shooting these same arrows at 285 fps with 6.5% FOC. After two hours of getting frustrating 5-6 inch groups at 60 yards, I finally woke up and decided to throw on my 125 grain tips to see what would happen. Immediately I got my 3 inch groups back at 60 yards with a new arrow weight of 468 grains at 278 fps with a FOC of 8.5%. Proves a couple of things to me…my bow likes a slightly softer spine arrow (which was gained by removing my 100 grain tips and installing the 125 grain tips), and/or my arrows needed a little more FOC at speeds over 265 fps. Note: The above groups were with field tips and mechanicals.