# How critical is it to have exact arrow weight to the grain?



## buckfeverben (Dec 2, 2004)

I don't buy that one for a second, one grain isn't likely going to make a 1 inch difference at 60 yards.


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## Jabwa (Dec 10, 2004)

I have read some things by Rick McKinney. Of the three factors (weight tolerance, straightness tolerance, and spine tolerance), he feels spine variation between arrows has the most effect on grouping. The other two are of much lesser significance. The manufacturers (except for Carbon Tech) do not provide us with spine tolerance data, however.


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## Jorge Oliveira (Aug 13, 2004)

Jabwa said:


> The manufacturers (except for Carbon Tech) do not provide us with spine tolerance data, however.


To me that says a lot about arrow spine consistency... :angry:


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## Bob H in NH (Aug 20, 2002)

A couple of years ago I read an article by Michelle Ragsdale where she was talking about things like this: exact weight, floating arrows to get the same side fletched etc. 

her opinion was, don't bother, it doesn't matter. Unless its something you will worry about, then it will matter cause you won't be focusing on the shot.

I figure if someone at her level can't tell, then why should I worry? :smile: 

--Bob


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## Chief P (Dec 1, 2003)

Do you weigh your glue? No. Don't worry about 2 grs. I'd worry if it was 10-15grs.


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## Smoke (Feb 4, 2003)

Bob, I might be mistaken but I doubt that Michelle was shooting all carbon arrows at the time she wrote that.  

Arrow drop is not nearly as extreme as some folks imagine. I used AA and a chrono and as I recall I found that a 5 grain difference in a 400 grain arrow out of the bow I was shooting made less than a 1" change in impact at 60 yards. Results at the target butts seemed to confirm the programs results.


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## Brown Hornet (Aug 8, 2002)

As long as you are within a couple grains don't worry about it. If your arrows are off by 10 grains then I wouldn't shoot them, but I don't worry about a couple grains. It is far more important to have a good spine match.


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## silverback (Jan 20, 2005)

Just a little fact. 1 grain is <0.3% of the weight of a 350 grain arrow.

That seems pretty insignificant. I don't see how it could result in an inch drop at 60 yards.


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## bfisher (Nov 30, 2002)

Take it from me. Anyone who can shoot well enough to tell the difference in POI at any yardage with 1gr variance does not have to work for a living. And theie house would be a showroom for every gold medal known to man.

Jabwa, Easton's tech manuals gives the spine variance for their ACC's at .005". I do agree about AC arrows though. I even emailed Carbon Express once with this very question and they hem-hawed around it.


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## niceguy (May 30, 2004)

According to Bernie's Idiot Proof Archery 6 grains will drop you 6 inches at 60 yards. I'm quoting from memory and I may be wrong as I don't have the book anymore. I'm sure someone will look it up.

regards


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## rooster61 (Apr 1, 2003)

bernie is on crack.

i did some calcs a few years ago. results will vary based on total arrow weight and initial speed, but using average figures, the amount of drop is about 1" at 90m per grain of difference.


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## 2ndchance (Sep 19, 2004)

if one grain made an arrow drop an extra inch at 60 yards that can only mean one thing. it slows the arrow down considerably. the weight while in flight makes no difference because everything drops at the same rate.

1 grain making an arrow loose approx 10fps+ is impossible.



Ty


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## silverback (Jan 20, 2005)

rooster is right, you can't judge the drop based solely on the yardage and difference in weight


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## Brown Hornet (Aug 8, 2002)

niceguy said:


> According to Bernie's Idiot Proof Archery 6 grains will drop you 6 inches at 60 yards. I'm quoting from memory and I may be wrong as I don't have the book anymore. I'm sure someone will look it up.
> 
> regards


The only way to Idiot Proof Archery is to take Bernie away.


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## niceguy (May 30, 2004)

Not agreeing or disagreeing with Bernie just quoting. For the record I don't believe a couple of grains has much effect. More important things to worry about.


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## Spotshooter2 (Oct 23, 2003)

> the weight while in flight makes no difference because everything drops at the same rate.


 For an arrow this is a false presumption. WHile yes things fall at the same rate if they are dropped straight down which and arrow is traveling parallel to gravity so weight difference will make a difference in rate of descent. Now do I think 1 grain will make a big difference , no and definitely not the way I shoot anyway. Would be interesting though to have a hooter shooter and a indoor environment where you could shoot them at the longer yardages just to put this question to rest once and for all. Now I do scale all my arrows to be within +/- .1 grain from top to bottom. Why , because I get bored and need something to do


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## Jorge Oliveira (Aug 13, 2004)

I have the TAP demo program, but I'm not used to it (just played a little bit), so this data may not be correct.

But according to it, shooting a 300g and a 301g arrows (all else equal), at 50m the difference in impact point is 0.31cm.


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## J.W. Shooter (Feb 15, 2004)

If you keep reading the book, it will tell you that the test was done at 210fps.! The faster the arrow is, the less difference it makes in weight! I have seen 6 arrows that weighed 9 grns. different from the lightest to the heaviest all go into the x-ring at 80 yds.! This was done at approximately 280 fps.!


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## srcarlso (Mar 3, 2005)

*Arrow*

I would not worry about 2 or even 3 grains - after my Hooter Shooter experience with group tuning, it seems nock alignment is more of an issue than weight as my POI changed 2" with a simple turn of a 3D nock in a Fatboy. If you have the time, find a Hooter Shooter and group tune.


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## 2ndchance (Sep 19, 2004)

Spotshooter2 said:


> For an arrow this is a false presumption. WHile yes things fall at the same rate if they are dropped straight down which and arrow is traveling parallel to gravity so weight difference will make a difference in rate of descent. Now do I think 1 grain will make a big difference , no and definitely not the way I shoot anyway. Would be interesting though to have a hooter shooter and a indoor environment where you could shoot them at the longer yardages just to put this question to rest once and for all. Now I do scale all my arrows to be within +/- .1 grain from top to bottom. Why , because I get bored and need something to do


the arrow is traveling perpendicular to gravity.

if it was falling straight down it would be parallel with gravity.

please elaborate on why you think that weight makes an object fall faster when it is traveling forward. 

everything falls at 3.14m/s/s until the object hits terminal velocity.weight has nothing to do with rate of decent. there is nothing to give the arrow lift.


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## Stash (Jun 1, 2002)

It is of course the effect of different arrow weights on arrow speed that's the issue here - gravity does not affect arrows of different weight differently. 

Here's another way of looking at the matter...

Using AA for the speed calculation, on one of my target bows a 332 grain arrow will shoot 250 fps. Adding 5 grains to that arrow lowers the speed by 1.5 fps

Let's say the target is 125 feet (42 yards) away - that means the 332 grain arrow will be in the air for .5 seconds (125/250) and the 337 grain arrow will be in the air for .503 seconds (125/248.5).

The heavier arrow will be dropping for .003 seconds longer than the lighter one.

3.14 meters is about 124 inches, so using the formula for gravity, in the .003 seconds the heavier arrow is in the air longer will cause it to drop .37 inches.

Now, this is just a rough calculation and ignores the decrease in speed downrange of arrows (using 250 fps as an AVERAGE speed rather than the exit speed), but we're looking at an order of under 1" drop at 40 yards for every 10 grains increase in arrow weight.

And on top of that, many people including myself have done *actual testing*. I've found that a 10 grain weight difference at 70 meters (ACEs at about 270 fps) causes about a 1-ring (on the FITA target) - that's about 3" difference in the center of my average groups.

I try to keep my under-300 grain target arrows within a 2 grain span, and that's for 90M. 

For 3D shooting to 50 yards with a heavier arrow and higher speeds, there is no way anyone could notice any significant difference between 2 arrows as much as 5 grains apart in weight.

To claim that an arrows drops 1 inch per extra grain at 60 yards is ridiculous. If that were the case, an arrow weighing 100 grains more would hit 8 feet lower!!!


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## silverback (Jan 20, 2005)

*gravity's effect on different weight arrows*

I agree with 2ndchance. 

But he might be assuming that the arrows are leaving the bow with no vertical velocity component. Say you are angling the bow up 15° to shoot 60 yards (estimation for the purposes of demonstration). if one arrow is going 200 fps (light arrow) and one is 300fps (heavy arrow), the initial components of velocity in the vertical plane are 200* sin (15°) and 300* sin (15°) respectively. This would be roughly 51 fps and 77 fps in the vertical direction respectively. Gravity would have to overcome this, and the 300 fps arrow would stay in the air longer because it has an initial positive velocity.

But I thinkg 2ndchance is still right, because, with today's fast bows, we are shooting pretty close to level. Even if we aren't, using the equation above 1 grain only turns out to make .25 fps of difference for the vertical component of velocity. This is all TAP does, so I won't bother doing the rest, since Jorge told us it only makes .31 cm difference.


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## Jorge Oliveira (Aug 13, 2004)

The conclusion by now is that 1g difference is not significant.

And I didn't post - but when I did the TAP simulation I did it both with 60# - and 40#. Same result, so it's not initial speed dependent...


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## Hollowpoint (Jul 10, 2003)

Chief P said:


> Do you weigh your glue? No. Don't worry about 2 grs. I'd worry if it was 10-15grs.


LMAO.  
My thoughts exactly.....I dont think ANYONE could tell the difference in impact between 1-2 grains.


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## 2ndchance (Sep 19, 2004)

stash- thats roughly what i was trying to say in a condensed version. i didnt think i would need to go through the whole process.


silverback- you are absolutly right. but like you said, when 10- grains is the only thing changing then the arrow trajectory will be roughly the same.


Ty


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## CarbonTerry (Jan 8, 2003)

There are a whole bunch of variables here. A 5 gr (for instance) variance is a much larger percentage on a 250gr target arrow (2%) than a 500 gr hunting arrow (1%). Accordingly the effect will be appx twice as large for the target arrow.

Gravity has no direction.

If you are taking the time to weigh your arrows, why not take the time to get the weights as close as you can to the same?

The REAL important issue here is........where does that difference in weight come from?
Is it the shaft, point/insert, nock, vanes, amount of adhesive used?
If it comes from the shaft there is probably a spine issue also. A different weight point/insert combo can effect the spine also. Nocks/vanes will change the FOC as will other components.
Ideally, the components should be weighed and culled for optimum performance/accuracy.
It is possible for the arrows to weigh the "same" but not to be able to group at long distance because arrow "A" has a 10 grain heavier point than arrow "B" that has a shaft that is 10 grains heavier and a point that is 10 grains lighter.
Most shooters will not want to go to these "extreme" levels to make sure that when they take that 18yard shot at Mister Whitetail everything is perfect.
To those of us who will, however, it is a great feeling when you are sure that every arrow shot will go exactly where it was pointed when the bow fires.

The tough part is pointing the arrow in the right spot everytime.


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