It doesn't matter whether the arrow is fletched or not. The totalarrow weight is 350 grains and the chrono is right in front of the bow so there is no speed loss due to fletching. That being said a bare shaft is probably used---one weighing 350 grains.

Not 5 gr/in. There aren't any arrows made that light. At least not any that would withstand the forces of a 70lb bow. The closest is HCA arrows that weigh 5.5 gr/in.

Like Arthur said, it isn't a standard or a specification like AMO is. AMO is a much more defined and more strict specification. It as an actual certified measurement. IBO is more of a marketing/ advertising ploy and can be fudged just like any other advertising.

IBO specs are a 350 grn arrow shot at 70 lbs with a 30 inch draw. However again like Arthur said they can take a bow with 70 lb limbs and a 30 inch draw module or cam on it and shoot it with a 350 grn arrow. However it's not uncommon for a bow with 70 lbs limbs to max out a bit higher, and many bows actually draw a bit farther than what the module actually states. This could give you an inflated IBO number. As well as shooting it with nothing on the string, or possibly even a string with less strands than what it will actually ship with or maybe a bit less brace height. In some cases that is just the best speed they got out of that particular model, not the actual bow you are buying. And if you read the fine print it says they can make changes to the specs during production.

And in some cases they can actually lie about the numbers since it isn't really a specification if they want to.

AMO specs are much more accurate, but not quite as impressive so you don't see them too much anymore. But the testing procedure is much more rigid and standardized.

Some companies do a great job of listing specs for bows, others are not even close sometimes. I know my Bowtech and Darton were pretty much dead on what they were rated at. The best thing to do is when looking at bows see if you can have them set up to fit you, then run an arrow or two through a chrono at the shop to see how each bow stacks up against the other. That is the only real way to know.

Paul

And I wholeheartedly agree with Arthur and Paul. AMO is a much more accurate measure in my opinion, and also is more indicative of a bow's average under most real life hunting conditions. Just how many hunters actually hunt with a bow set up at the conditions used to measure IBO speed........Very very few. AMO is just a truer measure, but as Paul said you hardly ever see it advertised anymore. Thats a shame.