# Great question for all you compound gurus



## THE JAMMER (Aug 1, 2005)

First of all I am not new to archery (50 years), but I am new to compounds- 2 years. I currently shoot a Mission Maniac set at 55#, 27" draw, and 380 gr arrows. The bow is an IBO 305 fps bow. I am getting about 250 fps at the 55# I am shooting.

The IBO standards are 70#, 350 gr arrow, and 30" draw. So I know that even if I pull 70# on that bow shooting the 380 gr arrows I shoot with only a 27" draw, I would not reach the 305 IBO speed.

If I bought a bow that was IBO 330 fps.- 25 fps faster than my Maniac, and set it at 55# ( the same I am shooting my Maniac now), would I see my speed 25 fps faster than the 250 I am getting now?

Or is the increase in speed only valid for the IBO standard of the 70# and 30" draw and 350 gr arrow standard they use for that measurement?

Realizing that my current 250 fps already takes into account my shorter draw length and heavier arrow (than pure IBO), the same parameters would be applied to the new 330 IBO bow.

If it is not linear, which I doubt that it is, what would be your best guess of my speed with the new bow??


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## THE JAMMER (Aug 1, 2005)

Well, I guess it wasn't a great question.


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## pevotva (Sep 7, 2005)

25 fps isnt even 10%. I would think you would be around 265. That said I also beleive that the IBO rating of bows is the least important of any of its numbers. Speed is VERY overrated IMO, people kill with 150fps longbows and recurves all season long. Razor sharp cut on contact put in the lungs or heart is where its at. If you are wanting to buy a new bow and need to sell it to yourself, good, but buy one that feels great not looks great on paper.


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## Capt. Marcus Canales (Aug 25, 2005)

if setting the new bow at 55#'s with a 27" draw, you will not see an increase in speed, unless you go to a lighter arrow...those IBO speeds are messured at 30" and 70 pounds for weight...

just a guess, but i'll ask my cousin what he thinks, he runs a shop here in town.


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## THE JAMMER (Aug 1, 2005)

The question is: same weight arrow, same length draw, same 55#

now getting 250 fps on a 305 fps IBO bow

What would I expect shooting the same arrow, same 55#, same draw length on a 330 fps IBO bow.

At IBO standards the difference is obviously 25 fps difference.


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## scrambler (May 28, 2004)

For estimating you can use this formula:

Add or subtract 2 fps for every 1 lb change from IBO in draw weight.

Add or subtract 10 fps for every inch of draw length from IBO.

Add or subtract 1 fps for every 3 grains of arrow or string accessory weight from IBO.

I've used this formula several times and it gets you pretty close.


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## devil1824 (Sep 4, 2010)

Technically it should be faster. Weather it is or not? Check out velocity arrows. My dad pulls around 50lbs. and shoots Velocity arrows and 75 grain points. Way lighter setup then I'm using. It's fine for deer. I wouldn't go that light on hogs though. Been there done that.


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## THE JAMMER (Aug 1, 2005)

scrambler said:


> For estimating you can use this formula:
> 
> Add or subtract 2 fps for every 1 lb change from IBO in draw weight.
> 
> ...


Scrambler,

Thanks that is what I was looking for finally.

According to your formula.

I would lose 30 fps from draw weight (70-55= 15 X 2= 30)
I would lose 30 fps for draw length ( 30-27+ 3; 3X10+ 30)
I would lose 10 fps from arrow weight (380-350=30; 30 divided by 3=10 10X1=10

Total I would lose off of IBO would be 70 fps off IBO of 330 fps.

So IBO 330 minus 70 = 260 fps. Which would be about 10 fps faster than my current set up.

I am going to try to get a shop to set a bow up, and take my chrono down, to check it out.

Funny. At IBO 330 of the new bow is 8% faster than the 305 of my current bow.
Yet at 55#, 380 gr arrow, 27" draw: 260 fps of the new bow is only 4% faster than 250 I am getting with the current bow.

this obviously shows that the vast amount of efficiency increase in the newer bow is in the upper ranges of parameters: weight, draw length, arrow weight.

THANX!!


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## Rack Ranch (May 25, 2004)

You should be about 10 fps faster with the new set up...Walker


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## THE JAMMER (Aug 1, 2005)

That's what I got.


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