Arrow Velocity How Fast Is FAST
GUN HUNTER TO BOWHUNTER
So you’re ready to take the big step and buy a new bow. You’ve spent time reading bow reports, checking-out ads in archery and hunting magazines, and talking to the sales people at the archery shop. Everything you hear and see is SPEED, FAST, and FASTEST. You’ve also noticed the arrow velocity ratings such as AMO or IBO F.P.S. (Feet Per Second). At some point you ask yourself the questions, "How fast is that....?, and just what do these speed ratings really mean?".
First, AMO is the Archery Manufacturer’s and Merchant’s Organization, and IBO is the International Bowhunting Organization. AMO is made-up of archery industry representatives (the people that design, build, and market archery equipment). IBO is an organization that conducts archery tournaments. When you boil it all down, AMO and IBO F.P.S. is the arrow velocity achieved from shooting an arrow through a bow, set-up with a formula that calculates what an arrow should weigh when shot from that bow. So neither formula was intended to compute arrow velocity.
How the formulas work:
The AMO Formula - To better understand the AMO formula, we talked with Gary Simonds of Mathews Archery. Mr. Simonds is a respected bow engineer and designer and serves on the AMO Standards Board. According to Simonds, the AMO formula calculates how much an arrow should weigh to be safely shot from a given bow and retain a good, safe transfer of energy, or bow efficiency. The formula uses the draw length and peak draw weight and ultimately arrives at a window of safe arrow weight for a given bow. AMO then selected an imaginary standard bow under which all bow designs could be tested for safety, durability, and accuracy, and there are no variables. That standard bow is a 30 inch draw, set at 60 pounds peak draw weight, shooting a 540 grain arrow, or 9 grains per peak bow weight = the AMO F.P.S. All of the manufacturers use this formula as a STANDARD in their research, development, and marketing.
The IBO Formula - Depending on whom you talk to, you get a different answer on the IBO formula. According to industry insiders, bow manufacturers forced IBO to institute some type of equipment limitation to create safer competition with fewer catastrophic equipment failures. If you have ever seen a bow blow-up, then you understand the manufacturers concerns - pieces can fly everywhere and injure the shooter as well as bystanders. The competition formula that IBO settled-on was a simple 5 grains of arrow weight per peak draw weight with an 80 pound limit on draw weight. Example: If you’re shooting a bow set at 70 pounds, your total minimum arrow weight for IBO competition would be 350 grains regardless of arrow velocity. The key to understanding the IBO formula is in knowing that it was developed for IBO COMPETITION, and only IBO competition.
This brings-up a very interesting point - today, archery competition requires a good balance of fast, dependable, and forgiving equipment. If you chose to use the IBO set-up, in most cases you will be shooting a very unforgiving, light arrow, and you will push the limits of your equipment unless you shoot very low poundage. For this reason, no other competition organizations accept this formula because it is too easily manipulated by competitors, and in most cases, it does push the equipment beyond safe design limitations. Other competition organizations (Archery Shooter’s Association, North American Bowhunters, and the National Field Archery Association) have arrow speed limits and other equipment limitations that create a level playing field for all competitors and resulting in much safer competitions.
Before you get the idea that we are slamming the IBO formula, remember that the AMO formula is very conservative and was developed in the time of the magnesium riser. Today’s exotic aluminum alloy, machined risers can take a lot more punishment, plus they are more efficient at transferring the energy to the arrow. Many of the manufacturers are asking AMO to change their formula to 6 or 7 grains per pound of peak draw weight to accommodate the new technology, but AMO can not make these changes as long as manufacturers continue to produce and sell magnesium riser bows.
A word of caution - When you see an ad that uses IBO F.P.S., most of the time they don’t tell you the draw length and draw weight of the bow, or the size and weight of the arrow used to create that velocity. It is important to remember that after the basic design of the bow, draw length is the biggest determining factor in arrow velocity. When you see these ads, realize that your results could vary tremendously depending on your draw length and draw weight. Plus the fact that the manufacturer may be stretching the truth a little, or a lot! Most bow manufacturers are making very accurate and dependable bows that will stay-together even while pushing them a little. However, many of the accessories such as sights, arrow rests, stabilizers, and scopes will fatigue and fail under such extreme usage. The 1997, 1998, and 1999 ASA Open Pro World Champion, Jeff Hopkins of Clayton, Delaware is one of the most respected archers in the business. He is also an extremely successful bowhunter, and firmly states that he would never dream of hunting with a bow that had been set-up for the IBO formula at 5 grains per pound, because the arrow would not have enough weight to control the broadhead, or cause good, reliable penetration.
A few more words of caution. Don’t let yourself get caught in a "bow speed-trap" - most bows that achieve IBO F.P.S. in excess of 300 F.P.S. utilize extremely reflexed risers and hard cam systems. Yes, they may be very fast and accurate, but because of the basic design most are very difficult for the majority of archers to control - what good is fast if you can’t hit where you’re aiming. Now before you buy that new bow, decide how you’re going to use the bow. Is it for competing in IBO tournaments, or is it to harvest an elk, bear, or deer? Now you can clear-up the confusion and give yourself an educated answer when it comes to arrow velocity ratings and bow selection.
