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Discussion Starter #1
I've been checking out some of the new bows this year and see they all have IBO speeds of 300+ fps. What are their requirement for getting a bow to shoot that fast? How do they measure their fps statistic?
 

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Discussion Starter #3
What do you mean by "no weight on the string"?

I understand the 5 gr/lb. But are you talking about peeps, kisser buttons, etc???
 

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IBO is a bow set at 70 lbs with a 30 inch draw and an arrow that is figured at 5 grains per pound so a 350 grain arrow. From my understanding no weight on the string means there is no peep sight, no kisser button, and basically nothing on the string. There are calculators to figure out what speeds you can get out of your bow. Lower draw weights and shorter draw lenghts will effect the speed you get. Weight on the string is another factor that affects speed. My bow has an IBO speed of 325 fps but I shot it through a chronograph and only got 282 fps. I have a 28 inch draw and my bow is set at 60 lb. Also my arrows weight is slightly over the 5 grains per pound and I do have a peep sight and d loop on my string that is extra weight.
 

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Discussion Starter #6
Thanks for the help everyone.

The reason I'm asking this is I am planning on using my Mathews Switchback as a 3D bow. It's a 70 lb bow and I thought it was only set to 60. So I took it into a bow shop and raised it to 66 lb. I'm shooting a 349 grain arrow out of it and getting 270 fps. The counter person at the bow shop told me to drop the weight of the arrow and stated that "IBO is 5 gr/lb". So that means I could drop down to a 330 grain arrow. I just wasn't sure how IBO measured the fps.

Thanks again.
 

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Keep in mind IBO standard is also the warranty limit for many manufacturers. AMO standards use a heavier arrow and therefore result in lower speeds. IBO is basically what a bow is capable of (from a speed standpoint) without blowing up/causing damage. The lighter the arrow the faster it may be but there are trade offs. Your bow will most likely not be as efficient and therefore more energy is transferred to the limbs/cams/string, etc. This will make the bow louder, cause hand shock/vibration, and shorten the lifespan of components. Some bows are rated to go down to 2 or 3 gr per pound but most are rated at 5. If you shoot below that given weight it will void the warranty and could cause damage similar to a dry fire.
 

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Discussion Starter #8
Good point, sendero. Yesterday I was watching one of my hunting shows and they shot an arrow that weighed something like 200 gr. out of one of the brand new Parker bows. It shot somewhere around 475 fps, but they reminded everybody not to do this to your favorite bow as they are not made to be shot like that.
 

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A lot of people don't understand how these advertised speeds are generated. They buy a new bow that is rated for say 330 fps and get really upset when they set it up and find it only shoots 280 fps. We sold a new Z7 to a guy this year who came right out and told us he was going to remove the monkey tails and string stopper as soon as he got it home and it better shoot 330 fps or else! He is a 30" draw and shoots heavy poundage but with the arrows he shoots he will never see 330 fps. My Z7 shoots 280 with my hunting arrows and 298 with my 3-d set up with a 29" draw and 61#. There are still a couple things I could do to jump it over 300 fps but it shoots fine where it is.
 

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Asajoe1 said:
A lot of people don't understand how these advertised speeds are generated. They buy a new bow that is rated for say 330 fps and get really upset when they set it up and find it only shoots 280 fps. We sold a new Z7 to a guy this year who came right out and told us he was going to remove the monkey tails and string stopper as soon as he got it home and it better shoot 330 fps or else! He is a 30" draw and shoots heavy poundage but with the arrows he shoots he will never see 330 fps. My Z7 shoots 280 with my hunting arrows and 298 with my 3-d set up with a 29" draw and 61#. There are still a couple things I could do to jump it over 300 fps but it shoots fine where it is.
You got that right!! What most people forget is a loop, peep or peep housing with a smaller apature, kisser, etc all take away from the speed. The only thing that nocks speed down faster than drawlength is arrow weight. It's takes some doing to get a target arrow down to 5 grains/pound of pull let alone a hunting arrow. Most people can't understand those factors.
 
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