# Best Arrow Combo, Speed - FOC - Spine



## Tattertot (Sep 14, 2007)

This will be shot out of my Switchback XT for an elk hunt later this year. I came up with these number using OT2. All arrows are Gold Tip XT Hunter using Nocturnal Nocks and G5 Striker broadheads.

Option 1:
5575 Arrow
100 Grain Head
27" Arrow Length
288 FPS
11.36% FOC
Spine is a Little Weak

Option 2:
Same as above but with a 28" Arrow looses 5 fps and is 10.04% FOC, also a little weaker spine.

Option 3:
7595 Arrow
125 Grain Head
27" Arrow Length
274 FPS
13.15% FOC
Spine is a Little Stiff

Option 4:
Same as above but with 28" Arrow looses 3 fps and is 12.88 FOC but Spine is A little less stiff.

The Questions of the day is: 

Is it worth losing 15 fps to have the stiffer spine, heavier arrow, and higher FOC?


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## alpinebowman (Sep 24, 2007)

Well I will tell you what has worked for me. I am shooting a xt 7595 at 27" with a 100 grain head with a FOC of about 10-10.5. It is shooting about 286 out of my alphamax with a 28" draw and it is also just slightly stiff which is far better for broadhead flight than a weak spined arrow. So with this setup you are getting your speed with a good BH spine,


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## TEX-O-BOB (Sep 12, 2007)

> Is it worth losing 15 fps to have the stiffer spine, heavier arrow, and higher FOC?


Absolutely!

The biggest mistake bowhunters make is sacrificing speed for stability. Speed means nothing if the shot is compromised by erratic arrow flight, crappy momentum, and poor penetration. Light fast arrows with no weight up front have all but three of these qualities.

NOTE: Notice I said "momentum" and not "kinetic energy" KE means nothing without some continued force after the arrow makes contact. "Momentum" is what makes good penetration possible. NOT KE. A heavier shaft will retain more energy downrange and through the animal than a light one. Simple physics... KE is how bullets kill, not arrows.


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## torowy (Jun 19, 2008)

Well really Momentum and KE are the same thing as far as an arrow is concerned.

They are both mass x velocity. Momentum is just KE over a distance.

A 100 grain arrow going 200 fps over 30 yards will have the same KE and momentum as a 200 grain arrow going 100fps over 30 yards.

Tatter, gold tip says that a FOC of 8-12 is best for hunting arrows. Either option 1 or 2 put you in that optimal FOC. with 2 being closer to the sweet spot. If everything is tuned correctly those arrows should fly with more stability. How does it affect the FOC if you shoot a 100 grain head on the stiff arrow?

What is your draw length and weight? If you are over 29 inches and over 65 pounds, you probably need to shoot the stiffer arrows.

Also, once you have your draw length and draw weight set. Your bow will shoot pretty much any arrow with the same energy and momentum. heavy arrows will just be slower than light arrows. but the arrow from 350-450 grains is going to do pretty much the same thing to the animal. There will be some variation from friction etc. but they will be pretty close.


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## TEX-O-BOB (Sep 12, 2007)

> They are both mass x velocity. Momentum is just KE over a distance.


True. But it is also a continuation of that energy specifically after it's passed through something. A more accurate definition of KE is what happens to that energy when it's transfered to another object. That's why bullets and arrows kill in different ways. A bullet kills by transferring the energy stored in the projectile to the target animal causing shock. The bleeding you get is just icing on the cake. An arrow kills by slicing as much tissue as possible causing massive hemorrhage and a loss of blood pressure that ultimately kills the animal.

Besides, after you get to so much poundage and arrow speed KE and momentum are a moot point. Todays C.M.A.S.D.'s are well capable of killing almost anything on the planet at 60 lbs. What it's really all about is how flat can my bow shoot, and how far can I kill a deer... :?


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## proutdoors (Sep 24, 2007)

Of the listed options, I would go with option 4 for deer/elk, if you are going after antelope I would go with option 1.


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## Riverrat77 (Sep 7, 2007)

TEX-O-BOB said:


> > They are both mass x velocity. Momentum is just KE over a distance.
> 
> 
> What it's really all about is how flat can my bow shoot, and how far can I kill a deer... :?


You'd die man... this is what I hear all day on the phone. "I want super light, super fast, weight is more important than spine (I cringe when that one comes up), what can I do to cut weight, how weak of an arrow can I 'get away with', etc". The one refreshing thing is that all the average joe hunters from the east coast who call in consider 40 yard shots pushing it... :lol:


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## MarkM (Sep 7, 2007)

Here is a link to a Fred Ashby article that talks about arrow penatration and the factors that go into it. Be prepared, lots of technical info.

http://tradgang.com/ashby/Momentum%20Ki ... ration.htm


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## torowy (Jun 19, 2008)

After reading that article, I am confused as to why the resistance to penetration only increases with higher velocity.

Also everything he talks about momentum, and how mass has more to do with momentum.... Momentum is just just mass x velocity. So 1 unit of mass is exactly equal to 1 unit of velocity.


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## MarkM (Sep 7, 2007)

torowy said:


> Also everything he talks about momentum, and how mass has more to do with momentum.... Momentum is just just mass x velocity. So 1 unit of mass is exactly equal to 1 unit of velocity.


It could be, and I am by no means an expert on any of this, that he says that becasue the formula for Momentum is mass X velocity as you stated. But Kenetic Engery is KE = (1/2)mv2 so the weight is divided in half in the formula for KE and the velocity is squared.

I agree with what Tex said above that KE describes the energy released at the target while Momentum describes how much force is required to stop an object from moving forward.

I know a lot of people in the Archery industry use KE but I think that is better suited to what a bullet does on game and how much shock it departs on an animal. Momentum is what you want in an arrow as you want it to keep going forward as long as possible when meeting resistance.

Interesting stuff and it can make your head spin trying to figure it out.

Mark

--------------------------------------------------------------------------------
cuts the


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## TEX-O-BOB (Sep 12, 2007)

Other things that impede or help penetration are drag, stiffness of spine, and how much weight you have up front. Ashby talks about extreme FoC and how it greatly increases penetration by reducing drag caused by an unstable arrow. Most guys are lucky to get 10% FoC out of their setup, when they should be demanding at least 15-20 % for optimal flight characteristics and stability during penetration. If more guys had more weight up front they would see a lot more stable flight in regards to broadhads too.


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## Riverrat77 (Sep 7, 2007)

TEX-O-BOB said:


> Other things that impede or help penetration are drag, stiffness of spine, and how much weight you have up front. Ashby talks about extreme FoC and how it greatly increases penetration by reducing drag caused by an unstable arrow. Most guys are lucky to get 10% FoC out of their setup, when they should be demanding at least 15-20 % for optimal flight characteristics and stability during penetration. If more guys had more weight up front they would see a lot more stable flight in regards to broadhads too.


So you think it would be worth throwing some 75 grain brass inserts in my Fmjs (I'd have to get new ones) to help stabilize my broadhead flight? I hadn't ever heard that so figured I'd ask. Does that apply more to a recurve setup than a compound?


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## TEX-O-BOB (Sep 12, 2007)

It's not just a trad thing. Extreme FoC works on any arrow because they encounter lower resistance. The reduced resistance results from less shaft-flex after coming out of the bow and on impact. Testing has shown shaft flex increases shaft-drag, and shaft-drag is a major influencing factor on penetration.

Extreme FOC arrows have at least three design features which reduce shaft flex on impact and create a more stable arrow in flight.

1. Less arrow mass is towards the rear, reducing the force with which the arrow’s rear “pushes” on the shaft. This is easier to understand if you think of super-gluing a brick to the point end of an arrow shaft. Now place the nock end of the shaft on the floor. Unless you keep the shaft absolutely perpendicular to the floor, the shaft flexes. Now, bump the shaft against the floor. Even when perpendicular, the shaft flexes at impact. Now, turn the shaft over placing the brick on the floor. The shaft does not flex. Bump it up and down. You can't see the shaft flex at all. This is a drastic example of how FoC effects an arrow.

2. Extreme FoC arrows concentrate arrow mass far forward. The forward lever arm is short. This means the dynamic center of pressure at impact is also far forward. To understand how this short lever with forward mass affects shaft-flex, think of the distance from arrow front to balance point as being a short section of shaft. The shorter the section, the stiffer it is. The stiffer it is, the less it flexes. That's why arrows with a low percentage of FoC will flex more on impact therefor creating more drag and impeding penetration. Plus, think about all these mechanical heads we're shooting these days that require so much force to open and become usable. Having a weak FoC with this type setup is the worst combination possible for good, stable, reliable arrow performance.

3. Having more weight up front allows for less required stabilization in th rear. When the forward lever arm is short, it takes less fletching in the rear to maintain good arrow flight. Now, you can get away with those 3 inch little girl vanes and still shoot a fixed blade head.


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## Snag32 (Sep 11, 2010)

In the archery industry the pendulum has swung too far to the fast and light side. I see some folks who own archery shops coming back into reality of a little heavier arrow to gain that all important momentum.
They do those penetration tests for bullets, I'd love to see that done for a heavy arrow vs a light arrow out of the same bow.


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## TEX-O-BOB (Sep 12, 2007)

Snag32 said:


> In the archery industry the pendulum has swung too far to the fast and light side. I see some folks who own archery shops coming back into reality of a little heavier arrow to gain that all important momentum.
> They do those penetration tests for bullets, I'd love to see that done for a heavy arrow vs a light arrow out of the same bow.


They have done it on arrows too. Dr Ed Ashbey did a complete study on arrow lethality and penetration and if you google it you can read the whole thing. Bottom line, a heavy arrow with about 10-13 grains of weight to every pound of bow being used to shoot it, coupled with an FoC of 18-25% and a single bevel, solid one piece two blade broadhead, will out penetrate anything and everything on all species of wild game from a deer to an elephant. Period.

My brother did his own study on an elk femur bone and a 50 pound recurve bow shooting a 650 grain arrow and a single bevel broadhead. This is what he found...


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## bwhntr (Sep 12, 2007)

Darin and I will never agree on his "theories" of momentum vs kinetic energy. I think it comes down to the understandings of the equations and how they relate to each other. Nonetheless, in the end it doesn't matter. EVERY bow manufactured kills and does it well. From the 40 lbs recurve to the 80 lbs compound, it doesn't matter. They all produce enough energy to push a stick deep enough into vitals to kill.

What is important is stability, and IMO this is most important for one reason...accuracy. I shoot a very fast bow (Mathews Monster). Where Tex and I do agree is weight, and also a good heavy FOC. I prefer the heavier stiffer setup, and I typically prefer 125 gr or heavier broadheads to get the FOC where it needs to be. It has nothing to do with speed or energy for me. If I shoot a 75 gr head or a 145 gr head they are both going to pass through most any elk I aim at. There is more energy in the heavier broadhead, but still plenty in the lighter. However, shooting anything lighter than a 125 on my setup and arrows start to dance in flight causing inconsistancies in the target down field. These "inconsisties" are not major but when picking what hair I want to split on my kill it can make a world of difference where I want to penetrate the vitals.

IMO, error on the heavier/stiffer side over lighter. You have more than enough speed and energy either way. At least stability and accuracy will be on your side. Good luck and have fun.


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## TEX-O-BOB (Sep 12, 2007)

> Darin and I will never agree on his "theories" of momentum vs kinetic energy.


"Theories"? C'mon guy! It's proven fact. That's why you believe it. Heavier is better. The end...


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## bwhntr (Sep 12, 2007)

Old smelly *******... :mrgreen:


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## TEX-O-BOB (Sep 12, 2007)

You left out bald, crotchety, short, and dirty minded...


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## Anaconda Pintler (Oct 29, 2007)

Shane it took me years to convince him about all the stuff he was just babbling about! Hell he even has a jig to drill holes in the center of wooden shafts now to place welding rod or other material as weight! Go figure I guess he got tired of watching me shoot thru everything I shot! o-||


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## bwhntr (Sep 12, 2007)

:mrgreen:


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## TEX-O-BOB (Sep 12, 2007)

Anaconda Pintler said:


> Shane it took me years to convince him about all the stuff he was just babbling about! Hell he even has a jig to drill holes in the center of wooden shafts now to place welding rod or other material as weight! Go figure I guess he got tired of watching me shoot thru everything I shot! o-||


 :roll:


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## stablebuck (Nov 22, 2007)

i think this is what a lot of eastern hunters are trying to account for with the lighter/faster arrow set up


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