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Thread: Can anyone explain what IBO and AMO means?

  1. #11
    Senior Member
    Join Date
    May 2009
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    Quote Originally Posted by Ehunter View Post
    Noone I know of hunts or target shoots with a tied on knock, and nothing else.
    I have a couple set up like that and all 3 of my wifes bows have only a tied on nock point and 1 'eliminator' button below the arrow nock.
    (the one 'button' does not change the chrono reading at all!)

  2. #12

    Default Can anyone explain what IBO and AMO means?

    Good point. BUT, IBO being in place for so long I doubt a change would come about.

    Still, I would go with just realistic draw length and draw weight and be happy. 27 or 28" of draw and 60 pounds of draw weight is far more realistic than what they have now. Speed is the word, so I'd go for a 300 gr arrow.

    Okay, all said within this thread so far, no matter what people would complain. Right now the factories are using a base bow. Start adding in X brand of this or that and people would cry; Why'd they use that junk peep, loop material or any other piece used to set the standard.

    The Speed Adjustment in my above reply works, if correct information is used. There are programs and archery sites with the automatic work sheets that work if given the correct information.

    I can figure it all day and come within reasonable speeds. And again, most bows will do claimed IBO speeds and more. My old 2000 Hoyt UltraTec is listed with IBO of 314 fps and said listed speed was said slow. It will crank 295 fps set to 62 pounds, 29 inches of draw and using a 314 gr arrow.

    70 - 62 = 8 times 2 = 16 --- 295 + 16 = 311 fps --- close.
    30 - 29 = 1 times 10 = 10 --- 311 + 10 = 321 fps --- over listed IBO.
    62 X 5 = 310 grs is desired IBO arrow weight.
    314 - 310 = 4 = 1 fps. --- 321 + 1 = 322.
    weight on string 22 grs = 7 fps. --- 322 + 7 = 329 fps. for finish.

    Now, I tried the next lightest arrow I had made up, 301 grs which is 9 grs too light for IBO specs. Chronographed my UltraTec nailed 301 fps (yes, 301 fps). So 13 grs lighter gave a increase of 6 fps. So dang near 1 fps for every2 grs. of weight. In other words the bow is more efficient than it should be and this a single cam bow. This bow is also finicky. If I let the specs go out velocity drops fast.

    Go back in time; Years back it was said to figure 1 fps for every 5 grs of weight. No doubt bows are getting more efficient.

    Also must figured each bow is different, ata, limb angle, cam system and whatever. Somewhere within the scheme of things a bow will perform great and at other points the same bow will perform to a lesser degree.

  3. #13
    Senior Member
    Join Date
    Oct 2009
    Boise, Idaho
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    I've kept detailed records on Martin bows I've had set-up for hunting, and numbers I use for my estimating are similar........changing arrow weight being the biggest varying factor on last 3 bows.

    10.0 fps = 1" draw length off base 30"
    1.0 fps = 3grs added to string
    1.0 fps = 4.2grs arrow weight within 6-7grs/lb off from base 350gr
    2.5 fps = 1lb draw weight from base 70lbs
    2009 Martin Bengal M2 Pro Cam w/factory STS & CCS.....66lbs, 29" DL, 422gr @ 272fps, Winners Choice string/cable, Trophy Taker drop-away Rest, Scott Release
    1996 Martin Firecat XRG Pro Series w/Ultra Sonic wheels.....69lbs, 29" DL, 465gr @ 245fps, w/fingers & Martin leather glove

  4. #14


    ok, not to try to kill this thread, ive actually learned alot reading this little thread. but who really cares about speed? i know, just about everybody. but usually with speed comes noise, the faster the bow the louder it gets, right? id rather have a slower than "average" bow thats as silent as i can get it. as long as im sighted in out to my comfortable range, and maybe one or two more pins, and im decent enough at range estimation(or i have a handy dandy range finder and ive mentally marked multiple markers in my lanes), then it doesnt matter if its shooting 500fps or 220. neither one makes the deer "deader" than the other.

  5. #15

    Default Can anyone explain what IBO and AMO means?

    Quote Originally Posted by thatguy View Post
    /// but who really cares about speed? //// it doesnt matter if its shooting 500fps or 220. neither one makes the deer "deader" than the other.
    Well, speed does have merit.
    First, it gives a idea of how much horsepower the bow generates. Whitetail deer are pretty puny animals, but Elk, moose, and big bears need some whomp. This said, big game has been taken with some pretty low poundage bows, but today more than ever putting down the animal quickly and humanely is paramount.

    Second, 3D is a game that needs some amount of speed to offset mis-judged yardages. The ASA has a base speed limit of 280 fps and it would be nice to know if after the build of the 3D bow that it would come close to the 280 fps. For local club 3Ds 280 fps isn't all that necessary, but when sanctioned shoots I want the best of both worlds, accuracy first and speed second. And I have competed in sanctioned shoots with bows that cranked as low as 260 fps and held my own. Beyond doubt another 20 fps would have been nice to have.

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