ibo vs actual speed

[DOPVFT]

Can any direct me to the link for this. I did a search here a few weeks ago found it no problem. Now I can not find it.
What I am looking for is the set of factors that I need to take into account for figuring out the estimated speed of my arrow based on my set upie subtract7 ft per sec for every inch my draw is under 30, subtract 4 fps for everything on the string.stuff like that.
Thank
Mike

[D.Parsons]

Mathews Inc.fourm.Has the exact information you need!

[zak123]

I use this formula:

Subtract 10 fpsfor every 1" you are under IBO length.
Subtract 1 fps for every three grains you are over IBO.
Subtract 2 fps for every pound you are from IBO.
Subtract5 fps for a peep site.
Subtract5 fps for a kisser button.
Subtract 4 fps for a string loop.

I used this formula and was off by 1 fps.

[Kanga]

I do it the easy way.



Acrono

[DOPVFT]

ORIGINAL: zak123

I use this formula:

Subtract 10 fpsfor every 1" you are under IBO length.
Subtract 1 fps for every three grains you are over IBO.
Subtract 2 fps for every pound you are from IBO.
Subtract5 fps for a peep site.
Subtract5 fps for a kisser button.
Subtract 4 fps for a string loop.

I used this formula and was off by 1 fps.

Thanks
I Only have a 27.5 in draw and am looking for a bow that the actual speed will be around 275+.
This really helped.

[BF1947]

ORIGINAL: zak123

I use this formula:

Subtract 10 fpsfor every 1" you are under IBO length.
Subtract 1 fps for every three grains you are over IBO.
Subtract 2 fps for every pound you are from IBO.
Subtract5 fps for a peep site.
Subtract5 fps for a kisser button.
Subtract 4 fps for a string loop.

I used this formula and was off by 1 fps.

I think about the only thing I would change/ add is that if you shoot a peep with a tube the figure is closer to 8-10fps loss.
Brass nockset--- 4fps loss each.

[Greg / MO]

Here's a copy of the actual thread you were referring to:

You can use the following to work backwards off listed IBO specs, this will put you pretty darn close to chrono:

IBO Specs - 30" draw/70lb draw weight and a 350 grain arrow.

For every inch of draw length you go down, you will lose 10 fps.

For every 5 # draw weight you go down you will lose 10 fps.

For every 3 grains of weight your arrow is over IBO (5 grains per pound) you will lose 1 fps.

For every 3 grains of weight you add to your string you will lose 1 fps.

[Paul L Mohr]

It veries with every bow, but the above figures will get you close. I think the bowtech manuals have some of it listed in them as well. Some bows are more effecient than others with different set ups.

To be honest, I just wouldn't worry about it. Shoot your bow the way you want to shoot it and take what you can get. Don't sacrifice something you want for a few extra FPS because you will notice it while shooting. The only difference will be on paper or thru a chrono. Too many people fudge thier draw length, shoot too much poundage or set thier bows up in a manor they don't like or are not used to in order to gain very negligable amounts of speeds. Then wonder why they can't that well. And then when you add the stress of hunting on top of it it really doesn't make sense.

Sorry for the rant, I know that isn't what you wanted. The above figures are pretty close to what I use. I agree with the above though, just shoot it thru a chrono. Find the bow you want, have it set up to fit you and shoot a few arrows thru a chrono while you are testing it out to see what it does compared to other bows. If this is not an option where you are buying your bow, I would look for a different shop. No way would I spend that kind of money without being able to compare different bows to each other.

Good luck,
Paul

[zak123]

I also have a 27.5 inch draw. My 70 lb, 27.5" 05 Bowtech Allegiance shoots 410 grain arrows at 273 fps.

[ejpaul1]

Ok, so I have a PSE typhoon rated at 298 (they say)and I am using a trophy taker drop away rest with a peep site. That is the only things on my string. With the right arrows, do you think I am maybe in the 275-280 range? Just wondering. EJ