i just bought a half dozen of arrows today and they said they was 8.1 grain per inch and i'm shooting a mighty mite vft 70lb draw and was wondering if the arrow will be heavy enough or too heavy i'm planning on using a 100 grain broad head any info will be highly appreciated thanks.

Grains per inch does tell us much. What is the length of the arrows when finished? Vanes or Feathers? For a decent setup you should be at least 350gr finished, but around 400 would be even better. What arrows are they anyway? Are they going to be properly spined for the length and bow weight? These are much more important than the arrow weight.

Im giving you a general figure assuming a thing or two you left out. But with 8.1 gpi and I "assumed" a 29 inch draw shooting a 29 inch arrow with 3 4inch vanes and at 70 pounds. I have calculated it to be 5.24grains per pound. IBO's lowest limit is 5.0 grains per pound. This should make you ok but leaning already towards the light side. Hope this helps some. Good Luck.
Whitey

Here's a tip, go to www.bowjackson.com and go to the FOC and Weight calculator. You should be able to find your arrow brand there and plug in the componenets you have. otherwise, you need to supply us with the following:

arrow length
arrow brand
vanes or feathers?
point weight

i'm sorry i left alot out i really don't know alot about this yet but the arrows are super carbon magnum arrows and we have not cut them yet but i have a 27 inch draw length so i'm assuming it will be about 27 inch arrow and my tip will be a thunder head 100gr. and i will be shooting vanes. the guy at the shop i bought them at said that those would be a good fast arrow i'm just worried about them being to light i hope this is enough info thanks for the help.

That puts you at exactly 5 grains per pound.

Correct me if I'am wrong but doesn't AMO recommend 6 grains per pound of peak bow weight? Deer Hunter I think you may be shooting a little light.

Warmdaze, yes AMO recommends 6gpp min....IBO recommends 5gpp min. Some bow manufacturers recommend as little as 5gpp, but some warranties are only good down to 6gpp or even more.

Almost forgot!

Using standard ICS components and 3, 3.875" vanes and the 8.1gpi that you supplied I come up with 5.4gpp.

Jason, Jason, Jason.... You've stomped all over one of my pet peeves. I must respond! [&:]

The truth of the matter is IBO does NOT recommend diddly squat. Ask them and they'll tell you in no uncertain terms. They have absolutely NOTHING to do with "IBO ratings."

A little history lesson...

In the mid-80's when 3D took off, people started going to overdraw setups on heavy poundage bows - 80 to 90 pounds or more - and very light arrows in order to achieve flat trajectories. Some guys were running as low as 3 grains per pound. Some even lower than that! When set up like that, the bows of the time, with their cast magnesium risers, laminated wood limbs, steel cables and teardrop string connectors, would flat explode after being shot for awhile. Some sooner, some later and some never would. Problem was, you never knew if or when those overstressed bows would cut loose. I knew several guys that blew up 5-6 bows in one summer!

People were getting hurt, even bystanders, by chunks of bows flying through the air. IBO finally had enough of the foolishness because they were losing participants to the emergency room and therapy centers. I know more than several guys who lost their front teeth and have many scars on their faces, chests and arms after being bashed with half a riser or lashed with steel cables and teardrop connectors. You can tell an old time IBO shooter from the number of scars on his face and arms - especially if he flashes a toothless grin at ya. [:-]

So, 5 grains per pound is a safety rule IBO came up with. It's not a recommended minimum arrow weight, it's merely the minimum weight they'd allow you to shoot in their tournaments. They basically said they'll let you be reasonably stupid. They'd let you rapidly wear your bow out, break accessories, pop strings and cables as long as your bow doesn't explode and hurt yourself and your fellow competitors.

THAT is what the 5 grains per pound stuff is all about. They do not 'recommend' you shoot an arrow that light. They're telling you that's as light as they'll let you shoot in their tournaments.

So, guys began setting their bows up with arrows at 5 grains per pound, shooting through the chrony and began talking about their IBO speeds.

Of course the manufacturers picked up on it and put their advertising agents on the job. Voila! We got "IBO ratings". It's nothing more than taking an arrow that weighs 5 grains per pound (the minimum under IBO rules) at 70 pounds draw weight (heavy as most people care to shoot) at 30" draw (taken from the AMO arrow speed/bow efficiency rating specification).

Then people began griping that they advertise IBO speeds but won't warranty their bows at IBO minimums. Some manufacturers said okay and did the warranty. Now folks are griping about bow prices. Well, now you gotta pay for that 5 grains per pound warranty.

So, please do not say IBO recommends shooting 5 grains per pound. Okay?