amo ibo rating

[lonewolf]

:? what's the difference between amo rating and ibo rating the bow i was looking at has an amo rating of 305 fps and ibo rating of 230fps and axle to axle length of 31'' iseem to like really short bows for some reason thanks for the help :D

[cdn-redneck]

Here is the way I copied it from www.thebowman.com hope this helps you out keep the questions coming we at bowzone.ca like to help out.

If you buy a bow thinking that you are going to use
your normal everyday arrow and shoot it at a comfortable draw weight and attain the IBO speed as
advertised, you will probably find that the arrow
does not go as fast as you expected, but you will be
able to attain the speed with a little work. Let me
explain by describing the two speed rating systems:

AMO - This rating has been around the longest:
Take any bow and set it at 60 pounds draw weight,
set it at 30 inch draw length, use a 2216 arrow cut
at 30 inches with a 125 grain field point.Shoot it
through a chronograph and that is your AMO speed
providing you have done everything accurately.

IBO - This rating reflects the speeds that the bow
is capable of:
Take any bow, set it at any draw weight and any draw length (the longer the draw length, the faster
the speed usually) - BUT the arrow used is made at
a weight of 5 grains per pound of draw weight
(ie:70 pound draw weight setting uses a 350 grain
total weight arrow).

Some things to consider regarding IBO speed:
1. These speeds are usually attained at a very
long draw length like 30 to 34 inches, much longer
than the average shooter's length of about 28 inches
with a release.

2. An arrow of 5 grains per pound is usually less
than some manufacturers advise. Also it is somewhat difficult to construct such a light arrow
that will fly consistantly.

The thing I like about IBO speed rating is that
it reflects what the bow is capable of, but keep
in mind that the average guy will probably not
attain these speeds under normal circumstances, at
least that is what I have found.

The thing I like about AMO is that these speeds
are attainable and easily surpassed by the
average shooter, it is actually a bit outmoded as
most shooters have less than a 30 inch draw length
(with the way today's modern bows are designed)
and do not shoot 2216's with 125 grain points,
although ten years ago, they did.

Now, just to clear things up so I don't get
attacked by the manufacturers - I truly belive that
most IBO speeds as advertised are attainable, because
I have attained them on just about every major bow
model. I am simply saying that the average archer
is probably not going to take the bow out of the
box and use the common recommended arrows at his
average draw length and draw weight and immediately
get that IBO speed. It will take some effort.

So use the ratings as a guideline and a comparison tool, but expect to do a little work
before your bow gets a chronograph reading with
those numbers on it.
The BowMan

[petew]

AMO
30" draw/60# draw weight. 540 grain arrow

IBO
30" draw 70# draw weight 350 grain arrow

Pete

[lonewolf]

:D thanks again every1 for the info. ive got tons of questions... so basically with some fine tunning these speeds are attainable..30''draw 65#draw weight easton 2213 xx75 arrows with 125 grain broadhead it is possble ?.... thanks again :D

[petew]

The ratings are done with nothing on the string.There are a guideline that rates bows against eachother.
As for the arrow that is suggested there is still a lot that is not accounted for.The weight of the insert can vary if you have aluminum[standard] or carbon inserts.Also the choice of fletching will vary greatly in weight.Feathers can be as light as 5 grains total and vanes can vary from a total weight of about 25 to 45 grains.
If you want to see if your bow will make the AMO / IBO speeds you will have to build and weigh an arrow to exactly 540 grains for AMO and, 350 grains for IBO , measure the draw lenght to exactly 30" , remove everything but 1 tied noc from the string and have an acurate scale to adjust the draw weight to 60 and 70 pounds respectively.Also you will need an acurate Chronograph .
If this sounds like a lot . it is.And you will only end up being dissapointed.It's not worth the bother.You should be fairly close to the advertised speeds with a well tuned hunting setup.Probably within 10 FPS with arrows weighing 540 / 350 grains.
Tune your bow well and it will perform well.
Does your car get the advertised milage?? probably not but you still are happy with it.