Would be grateful if someone can educate me with the 'formulas' used for calculating the AMO & IBO speed of a bow. I've used a laser speed meter on my bow and recorded speed (FPS) of different arrows, (carbons & aluminium)..but would really like to understand how this speed could be calculated using a formula. The draw length, draw weight, shaft weight/length must be all part of getting the speed of the arrow--but there must be a way of calculating this speed using a mathematic formula...isn't there?

try bowjackson.com i believe all the formulas are there.

AMO standard is 60# @ 30" w/a 540 gr arrow. That translates into 9 gr per #. IBO is 5 gr per pound: 60# @ 30" w/a 300 gr arrow. Those used to be the standards, I'm not sure if they've changed...

Thanks guys,your assistance really helped.

AMO has a new light arrow standard now, in addition to the old 540/60/30 standard.

360 grain arrow, 60 pounds, 30" draw.

None of the manufacturers use it though because it's an ASTM specification and they can't cheat like they do with the IBO 'thing'. I don't know what else to call the IBO speed rating, because it is not, and never has been a standard.

I've never concerned myself with IBO rating. I didn't worry about it when I shot compounds and I certainly don't worry about it with traditional bows. IBO shot at 5 gr/pdf? Give me a break.

For compounds, IBO used to be 70# @ 30" with a 350 gr arrow. Has it changed, or is it different for traditional gear?

Bill

Bill, don't look now but that's still 5gr per pound. <img src=icon_smile_big.gif border=0 align=middle> Was the IBO rating at 70#? Jeez, been so long danged if I ain't fergot! <img src=icon_smile_wink.gif border=0 align=middle>