IBO speeds

[over drawn]

Does anyone have the same problem i do?
I have Hoyt Alphamax 32 and the IBO speed is suposted to be 321 fps, but i just recently chronographed it at 207 fps. just wondering do any of you guys have that same problem?

[DocHolladay]

Are you shooting an IBO setup???

70lb draw weight
30" draw length
350gr arrow

If not, then I would say this is your problem. If you arent shooting at any of these measurements, then you wont see the speeds listed by the manufacturer. Of course, most bow makers over estimate the IBO speed to begin with.

If you are at these measurements and shooting that slow, I would look into your bows tune. Something is WAY out of whack.

[NYBuckhunter]

I agree with Doc, something isnt right unless you are shooting a 1000 grain arrow and a 25 inch draw lol

[johnstonab]

ok, I know this is an older post but i figured i would throw this out there.
advertised your bow shoots IBO 321fps.
so lets say you are like me and shoot 28" draw, 400gr arrow, still at 70lbs draw, string weight (peep, silencers, nocking loop) is 50gr


IBO Specs - 30" draw/70lb draw weight and a 350gr arrow.

For every inch of draw length you go down you will lose 10 FPS 28"= -20fps
For every 5# draw weight you go down you will lose 10 FPS

For every 3 grains of weight your arrow is over IBO ( 5 grains per pound) you will lose 1 FPS 50gr over= -16.7fps
For every 3 grains of weight you add to your string you will lose 1 FPS. 50gr= -16.7


321-20-16.7-16.7= 267.6fps

the string weight is a guess, i never weighed all mine. if you have 100gr string weight you speed would be around 250fps and if your bow is tuned down to 65lbs draw it would take another 10 fps off that plus a few FPS for the difference of draw weight to arrow weight. this is not perfect but it does let us see how all those gadgets effect arrow speed.

[09blackonblack]

Don't forget most manufacturers extend a bit past the backwall to squeeze every fps possible