IBO Speeds

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Lately, it seems that I am answering questions regarding the speed of new bows almost daily. Many people are of the belief that the speeds they see printed on the Internet or in manufacturer catalogues are the actual speeds that they will be shooting. This could not be farther from the truth. Let’s face it, speed sells bows. Everyone wants to shoot as fast as possible. Manufacturers play on this need for speed by printing ibo speeds.

The ibo test is a standardized means of rating speeds of bows. This test is conducted by setting a bow at 30" draw length, 70 pounds, and shooting a 350-grain arrow from it. This is the test that will produce speeds in the 300-325 feet per second range. While this test is a good means of comparing bows, it is not a good indication of how fast you will be shooting. First, not many people are actually a 30" draw length. For every inch of draw length you subtract you can expect to lose around 10 feet per second. This means that if you are around the average drawlength of 28" you can subtract 20 fps! Next, a 350-grain arrow at 70 pounds is five grains per pound. This is below the recommended minimum arrow weight for most bow warranties. Most companies will not guarantee a bow shot below 6 grains per pound. This means that if you are shooting 70 pounds you will need to shoot a minimum of a 420-grain arrow. This is a 70-grain increase in arrow weight. For every 5 grains, you can expect to lose a foot a second. This is an additional loss of 12-15 fps. Combine that loss in speed with the 20fps lost due to draw length and you have already lost 35 fps. These tests are also conducted on a shooting machine. You can subtract about 5 fps for the human release factor. These bows are shot without any accessories on the string. Some thing as small as a brass nock set can cost 3-5 fps. A peep sight can rob you of 5-10 fps. Silencers will subtract another 2-3 fps. All together, you can expect to lose around 10fps just setting up the string. This gives you a total loss of around 50-fps! This means that if you start with a bow that Ibo’s a 300-fps your hunting velocity will be around 250 fps. This is a terrific hunting velocity that most shooters will be able to handle comfortably. The fastest bows on the market today will shoot hunting weight arrows in the 260-280 fps range. These speeds will require a more experienced shooter.

So if you are looking at buying a new bow, do not let Ibo speeds give you a false impression of how fast you will be shooting. And remember accuracy is far more important than velocity.

Good luck and good shooting,

Seth

P.S.

The season is upon us. So, start shooting those broadheads!