I know that this has been gone over many times, but.... My buddy went and fully setup a Hoyt Vipertec...ready to hunt with and put it throught the chrono. He has a 30 inch draw and was shooting CX300's and the best they could get is 274 out of it. Hoyt's site says that the IBO is 300. lol Do away with all IBO ratings or atleast have independant tests done. To all new shooters....IBO ratings means nothing more than the paper it's written on. Gives you a ball park guess I suppose though. Ok..there's my vent for the day.

A fully set up bow is not to IBO specs. Ibo specs are useful to get an idea of how diffrent bows proform with the same variables. Adding a peep sight, string loop, kisser button, crimp on nocking points, string scliencer all effect the speed of the bow.

IBO is useful but for for figuring out what a hunting set up speed will be.

25 fps under ain't that bad.

As stated above - lots of things slow it down.

You have to know how heavy the arrow is.

I think we are all guilty of being too obsessed with numbers. That said I would like to see the manufacturers state ratings with a plus/minus, e.g. 300 +/- 9 fps. Some comapines use a range (which is the same thing as +/-) but I think ranges lead to some confusion. I work as a consultant for the pharmaceutical/biotech field and I deal mainly with validation of analytical methods and instruments. If you buy 200 mg Ibuprofen tablets, you are getting tablets that were formulated to a target of 200mg Ibuprofen +/- some percentage. The +/- comes from the variability of the assay used to test the tablets, usually around 2-3%. With bows I know there is some variability in the chrono, it also should be calibrated on a regular schedule, depends on the quality of the chrono but yearly is probably sufficient, but even the finest chrono is going to have to some variability. look in the manual, there should be a stated accuracy or reproducibility percentage in the specifications section. That means that any given reading could be off by that stated percentage, now add in the varibility of the scale to measure arrow weight, scale that measures draw weight, arrow lenght, bow string, shooter etc. Next time take your set-up and shoot it 6 times through the chrono, calculate the mean, then the standard deviation, then % relative standard deviation (%RSD) which is the standard deviation divided by the mean x 100. This is sometimes expressed as the coefficient of variability or CV. A scientific calculator (the calculator in windows is a scientific calculator) can do this in seconds. Then have someone else shoot six times and compare the numbers, especially the RSD's. You might be surprised how much variability there is for one shooter let alone two. I would be more impressed with a bow that had a low variability over some fantasic speed number, but companies know our love of numbers and speed rules so that is the first number everybody looks for, I know I do. To me, low variability translates to quality components, properly configured and assembled (something you and I should be less concerned about when plunking over $500 down for a bow). Sorry for the ramble but speed numbers are not absolute and as someone said, within 25 fps (under 10%) is probably not too bad.

PA257,

You going to have to "dumb" down your posts a little bit. Too many big words.

I hear what your saying though. Too many variables for just one # to be accurate in all cases and scenarios.

and tolerances...............LOL

Good post...thanks

An IBO rating is a useless factor to consider for bowhunting purposes. In fact, I believe the IBO rating is useless, period. Only an idiot or a misinformed person would try to use the setup that the manufacturers use to obtain the IBO.

Most bows made today will have all the energy necessary for the purpose of bowhunting. Final fps is dependent upon total setup and is strictly an individual result. Set your bow up for accuracy, reliability, and durability, and go hunting.

I have downed deer with my 156 fps and 172 fps recurves. For me, any fps above those speeds is icing.

Who was it that said: "I will take a slow hit over a fast miss, any day."

Missing IBO speeds doesn't bother me a bit, but in a related issue, missing the draw length really is poor, and most manufacturers miss the draw length - long, in order to play the IBO game. I wish they'd do away with the speed numbers. It doesn't mean a darn thing and I've actually witnessed people buying bows, based on the IBO figure. In my opinion, they're missing the boat, big time!

Used to be bow manufacturers listed AMO & IBO Speeds. I hardly ever see AMO speeds listed any more.

Just for the record, my bow is rated 320-328 IBO. The birth certificate listed a speed of 320 fps. This is right in the ball park considering that the birth certificate rating is obtained with a brass nock set, Bowtech silencers and Vibrablocks installed. All of this together robs approx 6-8 fps from the bow.

About the only thing I have trully found the IBO speed ratings for most companies' bows good for is a general comparison tool. Even then it is somewhat worthless because not all companies use the same "IBO rating" to determine their bows' rating. Some don't list the test specs at all and some just cheat the test standard by fiddling with draw length.