# Spine vs tip weight



## bowedup4 (Jul 17, 2011)

All, I'm looking to get some new field arrows, actually the GT Pierce. I currently shoot he pro hunter 340 with 150g tips. I feel my groups are a bit larger than they should be. I want to go down to 130. I shoot around 60 lbs and 30 1/4 draw. If I get the new arrows should I get the 300 pr 340. I'm not worried about being over spined just under spined. What tip whieght do you all shoot?


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## GRIMWALD (Sep 28, 2012)

I am a little on the cheap side, so I would first purchase a field point test pack,

http://www.alaskabowhunting.com/GrizzlyStik-Field-Point-Testbr-6-Pack-1-Each-P164C65.aspx

Then I would decide on weather I needed to change my arrows.

GRIMWALD


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## Chase Hatcher (Jan 30, 2012)

What makes you think it is the arrows? Just curious because I shoot pro hunter 400s with 150gn points, they shoot great. I've thought about going to the kinetics to see if it would reduce the couple glance outs I get.


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## Pete53 (Dec 5, 2011)

150 grain tips for field archery seems a little heavy ? buy the field point test kit, 100 -125 grains might be better ? I like 100 grain for my set up.i do use a 340 shaft too with g nocks and shoot a hinge.


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## grantmac (May 31, 2007)

Since you would be shooting a 29-29.5" arrow and making a whole pile of assumptions I'd be putting you into a .400 in the Pierce.

-Grant


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## TNMAN (Oct 6, 2009)

With your specs (and assuming shooting a Specialist), I'd be trying the 340's with 120 gr points.

All I know about the new Pierce arrows is what's on facebook. Look like good field arrows to me.

https://www.facebook.com/goldtiparr...7354075997267/993903090675690/?type=3&theater


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## Luke Cool (Oct 16, 2015)

To be heavy enough for a 60 pound bow, the arrow needs to be 300 grains or 19.44 grams. 
The less the arrow weighs, the faster it will go, the more noise, and the less kinetic energy. 
The heavier the tip is, the more spine you need. 
The heavier the game, the more kinetic energy you need . 
If you want a more stable arrow, stiffer shorter and heavier tips, are all good attributes.

Maybe its not the arrows fault, you may have more than one problem. 
Your bow might be out of tune, or you may also want to experiment with a better stabilizer and/or sight. 
Even your form and your health affects your aim.


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## Luke Cool (Oct 16, 2015)

Carbon arrow spine application chart









Too stiff is not better. The stiffness chart above tell the range that it is best to stay with-in.


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## Luke Cool (Oct 16, 2015)

Too stiff is not better. The stiffness chart above tells the range that it is best to stay with-in.
It doesn't show every scenario, for some, you will have to look at the trend.
When an arrow is released, it obsoletes at a certain frequency. 
In choosing the spine, you are choosing a application friendly frequency. 
The arrow's stability, has a lot to do with that frequency.
Being over spined is just as bad as being under spined.


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## gbeauvin (Sep 16, 2015)

Luke Cool said:


> To be heavy enough for a 60 pound bow, the arrow needs to be 300 grains or 19.44 grams.
> The less the arrow weighs, the faster it will go, the more noise, and the less kinetic energy.


I don't know much about archery, but I do know a little about kinetic energy. Velocity plays a larger role in energy than mass does, so reducing mass in exchange for higher velocity may actually increase kinetic energy. I'm not arguing for lighter arrows, though, just clarifying some physics.

-GB


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## Luke Cool (Oct 16, 2015)

gbeauvin said:


> I don't know much about archery, but I do know a little about kinetic energy. Velocity plays a larger role in energy than mass does, so reducing mass in exchange for higher velocity may actually increase kinetic energy. I'm not arguing for lighter arrows, though, just clarifying some physics.
> 
> -GB


That is a great question. I read a guide that tested this scenario. The results disagree with you. I'd like to share it with you.
http://www.huntersfriend.com/carbon_arrows/hunting_arrows_selection_guide_chapter_3.htm









In our example, the computed kinetic energy of the (5 gr/lb) 300 grain arrow was 49.66 ft-lbs. But when a 600 grain arrow was fired from the same bow, its computed kinetic energy was 54.16 ft-lbs. So doubling the arrow mass yielded another 9% in kinetic energy, or "knock down power." Obviously, all bows won't perform exactly as our test bow did, but you get the general idea - heavier arrows absorb more of the bow's energy (and carry more energy downrange). So if you want the added kinetic energy, you can shoot arrows at a heavy 10 gr/lb, just don't forget that to get the extra 9% in KE, you'll give up over 25% of your arrow velocity.
So before you make your decision in the speed vs. kinetic energy debate, you should consider your target - and the energy is takes to ethically harvest that animal with a bow. If you're hunting smaller athletic animals, say Pronghorn Antelope, which are particularly alert and skittish, a faster arrow would surely be best. Hunting smaller game doesn't require as much knock-down power, so getting the arrow to the target quickly will increase your chances of success. Other the other hand, if you're pursuing a 600 lb. Elk, you'll be less concerned about the animal "jumping your string" and more concerned about getting optimal penetration. So if you hunt large heavy game, a heavier arrow may increase your chances of success.


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## Luke Cool (Oct 16, 2015)

gbeauvin said:


> I don't know much about archery, but I do know a little about kinetic energy. Velocity plays a larger role in energy than mass does, so reducing mass in exchange for higher velocity may actually increase kinetic energy. I'm not arguing for lighter arrows, though, just clarifying some physics.
> 
> -GB


"Velocity plays a larger role in energy than mass does". This is untrue, if we look at the math, they are both equal.
In a vacuum, there would be no difference between velocity and mass. What you take from one, you will give to the other.
"Energy can neither be created or destroyed, it can only be displaced." *Albert Einstein
The bow releases the same amount of energy into a heavy arrow as it does a light one. But it does so in air, not a vacuum.
The test shown in post 11 can mean only one thing, something is taking more energy from velocity, than it is from mass.
Logically, the thief is the coefficient of friction. As we all know, the higher the velocity, the greater the air friction.
That, coupled the momentum created when there is a greater mass, velocity looses in two ways.


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## ppkaprince98 (Mar 13, 2008)

Luke Cool said:


> Carbon arrow spine application chart
> 
> View attachment 3079338
> 
> ...


How does the arrows GPI play into this. I understand the point weight, but overall arrow weight with the same spine should have some effect doesnt it?

Ex. 2 arrows with a 340 spine and a 100grain tip, one weighs 375grains the other weighs 500grains?


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## grantmac (May 31, 2007)

This is a forum for competitive field archery, if you lack the experience to contribute then please don't.

Grant


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## equilibrium (Oct 31, 2006)

LOL, Right. Buy a book, then read it. To many variables, plunger, brace height, string material...etc. Think of archery as a class and study. Then, you will find your fit. 



grantmac said:


> This is a forum for competitive field archery, if you lack the experience to contribute then please don't.
> 
> Grant


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## WhitetailAce (May 16, 2012)

So aside from the physic lesson and going back to your original question, the 340 would be the better spine if you are planning on running 140 or light points. If you continue to run the 150+ grain points then the 300 spine would probably be the better option. 

But if you are really looking to tighten up your groups then don't over look something as simple and changing your vanes and experimenting with different vanes. You will be amazed by how much making a simple vane change can affect your groupings.


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## Luke Cool (Oct 16, 2015)

ppkaprince98 said:


> How does the arrows GPI play into this. I understand the point weight, but overall arrow weight with the same spine should have some effect doesnt it?
> 
> Ex. 2 arrows with a 340 spine and a 100grain tip, one weighs 375grains the other weighs 500grains?


This chart is from Eastmen. A carbon arrows spine is determined by the thickness of its tube's wall. Carbon is carbon, and the grains per inch is fairly uniform at a given thickness, even on arrows from different manufacturers. There will be little differences, but not like in your example. This chart was only meant to be a general guide, and it serves this purpose well. Length is a factor, but this is addressed in the chart..


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## Luke Cool (Oct 16, 2015)

There are no stupid questions. If we are not all here to learn, what is the purpose of any forum. 
Please encourage all contributions. The physics lesson is not wasted space, more than one person will learn something from it. 

I am 60 years old and want my bow to be comfortable for more than one set of arrows. Because of this, my bow is set at 54 pounds.
I use a 350 carbon arrow, with a 75 grain tip. This is a very light arrow, but I can shoot some tight groups with it.
The target bow I do this with is made by Bowtech.


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## TNMAN (Oct 6, 2009)

From earlier posts, still assuming OP is shooting a Specialist, which ibo's at 330 fps. The 340's will allow you to use enough point weight to stay safely below the nfaa 300 fps speed limit, and should spine nicely with good foc. Not saying 400's couldn't work, but will likely run out of spine unless cut short and shooting a fairly light point, which would then put you over the speed limit. Still thinking .340 will work best. I honestly don't know much about the Pierce arrow yet, or how it actually spines out. Just my best guess. ---> p.s. Get enough weights to bump up above 120 gr as necessary. I think GT has made a very nice field arrow at a fair price, and thinking about some of them for myself.

And yes to Grant. I have shot decent field scores. Have gotten older, and sort of banged up right now. Hoping to get better before next outdoor season. Sorry if I ruffled any feathers by recommending the .340's. I really did think about it before posting.


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## equilibrium (Oct 31, 2006)

So, is this a question to one or all? Is it "Any of your guys"......or.........is it "Any of you guys"??

"Any of your guys shoot Field at a competitive level?"


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## grantmac (May 31, 2007)

TNMAN said:


> From earlier posts, still assuming OP is shooting a Specialist, which ibo's at 330 fps. The 340's will allow you to use enough point weight to stay safely below the nfaa 300 fps speed limit, and should spine nicely with good foc. Not saying 400's couldn't work, but will likely run out of spine unless cut short and shooting a fairly light point, which would then put you over the speed limit. Still thinking .340 will work best. I honestly don't know much about the Pierce arrow yet, or how it actually spines out. Just my best guess. ---> p.s. Get enough weights to bump up above 120 gr as necessary. I think GT has made a very nice field arrow at a fair price, and thinking about some of them for myself.
> 
> And yes to Grant. I have shot decent field scores. Have gotten older, and sort of banged up right now. Hoping to get better before next outdoor season. Sorry if I ruffled any feathers by recommending the .340's. I really did think about it before posting.


It wasn't you I was addressing to be honest, your recommendations are totally inline with what I've seen dsome great shooters using. I was more concerned with those who think you absolutely can't get a .400 to fly from a 60# bow. The initial post i made indicated making a bunch of assumptions to arrive at my figure. One was that a 6.5gpp arrow wouldn't be breaking the NFAA speed limit and if it did a small tweak down in draw weight would fix that. Then again I always tune my bows a few pounds under max to have wiggle room.
If he can keep a .340 with a heavy point above 280fps then he should run with it.

Grant


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## montigre (Oct 13, 2008)

equilibrium said:


> So, is this a question to one or all? Is it "Any of your guys"......or.........is it "Any of you guys"??
> 
> "Any of your guys shoot Field at a competitive level?"


Yes, but I'm not a "guy" and there is always room for improvement; especially with field archery..... :wink:


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