tfox, by the time the arrow was in the chrono - the bow is out of the equation - it isn't even a factor is it? how would that fit into the equation? i don't think it does - i think artp is on the money again.
i can tell you i'll be building my 3d arrows a little differently this year.

so are you guys saying a 600 gr. arrow traveling 250 fps has a flatter trajectory than a 415 gr. arrow traveling at 285fps?

Aruthur P - interesting article. You will note that there is no mention of arrow weight as being a factor in the arrow's flight, once it leaves the bow. This is also the case in rifle bullet ballistics. If a 100 grain 6MM bullet has the same ballistic coefficient as a 200 grain .30 caliber bullet, and they have the same muzzle velocity; they will fly the same out to infinity. Central principle of ballistics. Timeof flight is what matters, and that is controlled by the ballistic coefficient of the projectile as well as the initial muzzle velocity.

At distance. It may not be realized until after 40 yards but yes, at 80 you will see a definite difference.

True, except for the fact that you are comparing apples and oranges. Same ballistic coefficient, yes. But you have to reduce the size of bullet to retain that same coefficient. Change that 100 gn bullet into a .30 cal like the 200 gn, and you've changed the sectional density dramatically, which also drastically changes the ballistic coefficient.

Fortunately, our arrows are hollow. That gives us some real opportunities to customize our arrows according to our needs. We can change the sectional density of our arrows to improve their ballistic coefficient by adding weights.

We want to improve long range trajectory, or we need better energy retention for better penetration on larger or tougher game, or to shove a broadhead with a large cutting diameter through? No problem.

So, we slide a weight tube inside the shaft, or use brass or stainless steel inserts, or maybe bump up to a 200 gn point instead of a 100 gn point. Or maybe we do ALL those things. And there it is. We've increased the arrow's sectional density and improved it's ballistic coefficient without altering the arrow's diameter or profile at all.

But bullistic coef is not exactly drag coef, or friction coef. bullistic coef is a matters efficiency to reach a target, and thats where momentum and wieght is a factor.Not just the shape of the bullet.People get bullistic coef and drag confused. Or think they are the same thing, and they are not.

Mark - if you study the various charts/programs used to calculate the trajectory of a bullet, you will find that the weight of the projectile is not really a factor in the equation. Although, generally, heavy bullets have better B.C.'s than light bullets; there are some very long slender bullets in the .22 and 6MM calibers that have B.C.'s comparable to the larger bores - and, in that case, they shoot just as flat - sometimes flatter, since their initial velocity is often higher.

What I hear being argued here, in principle, is that a given diameter arrow would have more drop at close range, but less drop at long range, if you made it heavier by adding some weight to the inside of the shaft. And I'm saying that the initial velocity will go down because it is heavier - and that it will never recover that velocity over distance because the ballisitic coeffcient of the arrow never changed. All that changed is that you had to move the 20 yard pin down a little to compensate for the slower arrow; and subsequently altered the upward arc of the arrow's flight.

Remember,when you increase arrow weight you increase momentum RIGHT,we agree on that therefore you are seeing less loss of energy.


The same thing happens when you increase the energy source,The longer draw or heavier poundage produces more momentum.



If you shoot the lighter arrow out of your bow it will have more momentum than it does out of his bow so there is no way you will experience as much of a loss of speed than when comparing 2 different bows with 2 different arrow weights.


You will see a slightly higher percentage of speed loss from the heavy to the light arrows from the same bow but no where near the percentage loss when comparing 2 different bows with different amounts of stored energy.


Now I can go back and read the rest of the responses.

Tom Crowe a long time 3-d pro shoots ASA with an 80# bow and will setup the heaviest arrow to get 280 fps.


The whole reason is to get as much momentum as possible.That is why he uses 80# and shoots a heavier arrow.


A 60# bow will not yield as much momentum shooting the same 280 fps.Provided they are relatively the same in ibo ratings.

it won't produce as much momentum only because the arrow is lighter.