The Importance of FOC and Arrow Flight for Hunting Whitetails
The shot landed exactly where I wanted it too. I had spent months preparing for this single moment in time when a 75 yard shot would present itself and I would unleash my 416 grain arrow through the large timbered clearing and sent thundering towards a whitetail deer, that stood broadside, eating in one of my favorite food plots. All the time spent shooting out to 100 yards, and practicing in the humid summer heat, knowing that this shot might present itself was now worth it. All the work I did in the off season just paid off with a single shot that passed though both lungs and the whitetail doe that ran just 35 yards after the shot and collapsed. Without a properly balanced Front of Center (FOC) arrow this shot would not have been possible.
The importance of FOC in arrows today is one of the most debated topics within the archery industry. Industry experts not only disagree about the various percentage of FOC that hunting arrows should have, but even how to calculate it. Add to that the amount of misinformation on the internet, and it is no wonder so many bow hunters are confused about FOC. What is FOC? FOC describes the percentage of an arrow’s total weight that is located beyond its physical halfway point. My current setup of a Carbon Express BLU RZ has a FOC of 13.79%. I have a 29 inch arrow with a 125 grain broadhead. The center point is 14.5 inches, and the balance point is at 18.5 inches. Now when I use a 100 grain broadhead, my balance point changes to 17.5 and my FOC changes to 10.34%, which is still acceptable by all standards. Luckily both of my setups, fall within the sweet spot of 10-15% as recommended by the Technical Guidelines published by the Archery Trade Association (ATA) for hunting FOC range. However for optimal penetration, I should be shouting shooting a 125 grain setup. Here is how I calculate FOC.
Find the middle point of your arrow shaft by measuring its length from the valley of the nock to the cutoff point at the front of the arrow and divide by 2. Mark this point on the shaft and write down the number.
Next your will need to the balance point of the arrow. The arrow shaft should come to rest parallel to the ground below. Measure from the valley of the nock to the balance point.
Now you will need to subtract the center of the arrow measurement (taken in step 1) from the balance point.(determined in step 2)
Multiply the difference of those numbers by 100
Finally divide the product determined in step 4 by the arrow’s overall length and this will give you the FOC percentage of your hunting arrow.
Now that you have your FOC percentage, how does it affect arrow flight when you are hunting whitetails? If your arrow has too much FOC it was nose dive quickly, too little FOC and the back end of your arrow will waggle more than the backside of a waddling duck. If you are only taking shots inside of 30 yards, the FOC will not have a significant impact on your shot, however when you increase th e distance of the shot and/or add in a crosswind, FOC becomes very important. For hunting, if your bow has an FOC of 10-15% your arrow will be more stable in flight. Because your arrow is more stable in flight, you will get better down range accuracy and down range penetration. You might have to sacrifice a little speed for a proper FOC setup, however today’s modern compound bows have speed to spare.
For any whitetail hunter looking for the ultimate in arrow performance, take some time to determine your FOC and see what it will take to get your arrow in the 10 to 15% slot. Ultimately your goal should be to get your arrow to 10-13% FOC, for maximum performance. If you cannot get your arrows into the 10-15% sweet spot it is time for new arrows. When it comes to buying arrows, you get what you pay for. If will be well worth your time and effort, especially when you are taking the shot of a lifetime.