# AMO vs IBO speed



## cream (Mar 7, 2004)

Didn't speed ratings used to be measured as AMO? Now it's an IBO rating. Seems to me there is a 50 to 100 fps difference. Any body got a rule book or whatever to explain this?


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## p8ntballnryan (Apr 5, 2003)

i forgot who does what. I believe ibo measures speed at with a 5gpi arrow at 70#@30" where amo measures it at 28"@60 with a 9gpi arrow.


looking at it now i think i'm wrong but it's something along those lines


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## kc-griz (Apr 22, 2003)

Copied from an old post on another forum:

A.M.O.(Archery Manufacturing Organization) and I.B.O. (International Bowhunters Association) both have a method for testing arrow speed from bows and although they are different both can be used to compare equipment for relative speed. 
Both of the speed testing standards use a constant drawlength, arrow weight and bow weight to test bowspeed. These are the way the two differ.
A.M.O.
Under this standard the bow being tested will have a maximum pull weight of 60lbs. The arrow will have a grain weight of 540(9 grains of arrow weight per pound of bow weight). The draw length will be set at 30 inches. The chronograph used for measuring the speed will be placed at point blank range for testing.
I.B.O.
Under this standard the bow being tested will have a maximum pull weight of 70lbs. The arrow will have a grain weight of 350(5 grains of arrow weight per pound of bow weight). The draw length will be set at 30 inches. The chronograph used for measuring the speed will be placed at point blank range for testing.
What is important about these two speed ratings is that they are only to be used to compare bows speed tested under the same standard. They should NOT be used to tell you what you will personally shoot for speed. For example lets take an average archer……Bill Bowshooter……..Bill has a 29 inch draw length shoots his bow at 65 lbs and shoots a 455 grain aluminum arrow. In our example neither the A.M.O. or the I.B.O standards will accurately reflect the speed of Bill’s bow. Since Bill is shooting a shorter draw than both standards, shooting an arrow that weighs 7 grains of arrow weight per pound of bow weight, and is shooting 65 lb peak weight he will shoot at a speed very different to either standard.
If we try to make some generalizations about the two different ratings we could say that the I.B.O. speed rating is much faster than most archers could achieve, and conversely the A.M.O. speed rating reflects a speed that is less than what most shooters could achieve with the same bow. If a bows I.B.O. speed rating is 320fps and its A.M.O. speed rating is 245fps that would mean the average archer would shoot that bow somewhere in the middle of that range.


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## p8ntballnryan (Apr 5, 2003)

see....papa bear knows. lol i was close!


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## cream (Mar 7, 2004)

I totaly understand and agree with your explanation. I was asked by a bunch of shooters at the local shop to find out what AMO/IBO speed was all about. It seems to me that the IBO speed rating is an advertisement Gimmick. With your permission Griz, I would like to print your explanation and post it at the local shop. CHIP


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## kc-griz (Apr 22, 2003)

feel free to post it... I had it saved in my files from a couple years ago and really don't know who to credit it to.


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## Ossage (Dec 11, 2003)

That explanation is wrong though, unless there have been some major changes to the IBO side of things. I haven't competed in about 5 years since having everything from the waist down crushed. I am a bit out of touch. Still here goes:

IBO does not have a bow rating system (last I heard). They have a rule that limits bows that enter their comps to either 5gr/per pound minimum arrow weight (or under a more recent addition 280 fps with lower still arrow weight).

In context, IBO was the first big thing in 3D archery. I don't know which of many tours is now the biggest, but in it's day, the 5 grain rule was a significant factor both in driving bow performance and bow reliability. More recently the 280 rule with or without 5 grain rule seems to be being picked up by more tours.

The 5 grain rule as a standard is important because it shows what the bow performance with light arrows is like. Many shoot these bows in competition, and some even to hunt. Also, it is easier at times to estimate 280 performance off the IBO number than the AMO (now called ATA?)

The AMO number is the Johnny come lately. The AMO didn't want it's members hit with liability suits off broken bows, so set their number off of higher arrow weights. 6 grain arrows are kind of a no man's land too heavy for most 3D, and too light for most hunters, though of course that is changing. But AMO is a bow rating standard. It does specify draw length and bow weight. There was nothing to stop a crooked manufacturer from giving an IBO rating of 320 fps having shot a bow at 80 pounds and 33 inches, Which is why most ads specify 70 pounds and 30". But that is a convention, not a standard (last I heard).

The IBO isn't a gimmick it's part of competition rules. The AMO/ATA is a bow rating standard. Significantly both would be terrible ways of rating traditional bows.

With Mathews compounds shooting a release, with factory serving, and at the time a 3MM loop style nock, a peep, I consistantly have shot 305 fps on bows IBO rated at 310. At the time I was shooting 70# and 30", and wasn't playing any tricks with the valley. Seems pretty representative to me. I've competed in 3D with about 9 compounds, one a very nice Hoyt Intrepid. Up here there is a velocity limit of 280, so I have to measure them, and measured them both for IBO, and then for 280. They were all real close on IBO ratings. I've never checked the AMO rating because it isn't good for anything.


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## p8ntballnryan (Apr 5, 2003)

> IBO does not have a bow rating system (last I heard). They have a rule that limits bows that enter their comps to either 5gr/per pound minimum arrow weight (or under a more recent addition 280 fps with lower still arrow weight).



no sir...ibo does have a bow rating system. Whenever you go shopping for a bow people will always tell you the ibo speed instead of the amo to make it sound amazingly fast to the customer. What you stated i THINK was IBO rules for 3d tourns regarding bow speed and level playing fields.


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## Ossage (Dec 11, 2003)

"no sir...ibo does have a bow rating system. Whenever you go shopping for a bow people will always tell you the ibo speed instead of the amo to make it sound amazingly fast to the customer. What you stated i THINK was IBO rules for 3d tourns regarding bow speed and level playing fields."


That's the point all there is are the IBO rules, the fact that people say stuff like "most used softdrink in Nascar" doesn't mean NASCAR has a softdrink rating system. IBO has a public site, and a HuntingBBs group, if you can show me where this IBO rating system exists then all I can tell you is it's new. Baring a change in the last 6 months or so, there is no such thing as IBO ratings.

It absolutely is the case that manufacturers use these numbers, and it's good publicity for IBO. It's also significant to any buyers shooting IBO who all want the highest possible velocity for a legal arrow weight and a given degree of accuracy. Though since IBO started scoring the X's most don't shoot highest velocity any more. Sign of the times.

Also, as mentioned, the IBO came out about 10 years before the AMO, so while the IBO might look like an attempt to make a faster looking rating velocity, it was in use for years. During those years the AMO was complaining that 5 grains wasn't safe despite the evidence of billions of safe shots by 3D shooters. So when they came out with their rating they had to put out a slow one or look like fools, but it isn't really a useful number.


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## cream (Mar 7, 2004)

I didn't mean to start a war. When I was involved very heavily in archery ( tournaments ) in the 70's there were two organizations. NFAA- compounds ( sticks were allowed ) and I can't remember the other one, but they didn't allow compounds. AT that time it was mostly 4 wheelers but the 2 wheelers were knocking very hard at the door. The magazine adds touted the blazing speeds of these componds. 2 & 4 wheelers. 205fps,210fps, etc. Standing at a 60yd target one day with Frank Gandy ( my state of the art compound against his recurve ) it was very obvious my arrows were much faster than his. On my best day I couln't come close to Frank, or Ed Eliason for that matter. I learned then that speed was no big deal. I totally dropped out of Archery for 30 years. Now I'm back shooting a Martin Stick and having more fun than I ever did in the old days. Of course every body I shoot with has a state of the art compound. That's how this whole advertising arrow speed thing got started. I don't no any thing about tourny rules,regulations,etc. All I know is the advertised bow speeds of today are not 100fps faster than the advertised bow speeds of 30 years ago. Thanks Chip


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## Fin (Mar 20, 2004)

The confusion seems to be in the difference between "IBO" speed in terms of a sales brochure for a bow..and "IBO" speed in regards to competing in an IBO sanctioned tournament. Back in the day when bows were slower and 3D wasnt such a big deal, companies mostly gave the AMO (archery manufacturers organization) speed, which rated a bow @9 grains per pound and 30 inches of draw @60 lbs of weight. (I think thats the setup anyhow) Now that bows are often designed for hi-speed and 9 grains per pound is overly conservative in terms of limb stress (Yes the AMO didnt want lawsuits) most companies only give an "IBO" speed. The only constant Ive seen in IBO rating is the 5 grains per pound that also applies to tournaments. Ive seen [email protected] 30 inches..32 inches..60#..70# and 80#. My Champion compound has a rated IBO if about 310 fps. The AMO would be around 240-245 fps. I take advantage of the local rules of =/- 5% or 288 fps and shoot it around 286 fps. Given that I draw 28" and pull 58 lbs..Im not going to reach the "IBO" speed for my bow. Each inch of draw under the rated length is good for about 5-7 fps depending on the bow. So basicaly.... not all 5 grains per pound are created equal. Look at the fine print and see how the bow was tested in terms of length and poundage.


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## p8ntballnryan (Apr 5, 2003)

i'm talkin about ibo speed on the sales brochure. to my knowledge they get there super fast numbers off of 70#'[email protected]" now adays with a 5gpi arrow. i'll ask the folks at the shop tomorrow. I do know that the ibo has rules for shoots but they do also publish speed ratings for most if not all bows nowadays. just look at your next bow catalog. Hell basspro and cabelas list the amo and ibo speeds of the bows they sell online.


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