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Can you over spine high FOC?

MattMan81

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Jan 13, 2020
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Just curious. Looking at trading for momentum shafts. Currently running a 250 Apollo. 28.5" OA, 680is taw. 200gr up front.
If I went to a momentum 170 shaft will I get over spined problems? What's the down side? Will a more rigid arrow be less forgiving?
 
Just curious. Looking at trading for momentum shafts. Currently running a 250 Apollo. 28.5" OA, 680is taw. 200gr up front.
If I went to a momentum 170 shaft will I get over spined problems? What's the down side? Will a more rigid arrow be less forgiving?

Generally speaking, it’s pretty hard to have a shaft that’s too stiff when tuning a modern compound but…170, that’s pretty stiff! Have you run the numbers through any software to see if you’re in the ballpark?

You’ll need to provide more detailed information to enable someone to give you advice on this without completing guessing.

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Also, this part about forged broadheads had me a little worried about switching to the 170.

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Just curious. Looking at trading for momentum shafts. Currently running a 250 Apollo. 28.5" OA, 680is taw. 200gr up front.
If I went to a momentum 170 shaft will I get over spined problems? What's the down side? Will a more rigid arrow be less forgiving?
What animal are you hunting in the US that requires you to run that shaft? Or is this just for experimental purposes?
 
I would not think you would need to go that stiff unless you were building a very heavy arrow, like in the 900+ grain range. 250 should be plenty heavy. The problem with FOC and stiffer spines is that the stiffer the spine, the heavier constructed the shaft has to be and that adds weight to the grains per inch. That adds weight all along the arrow robbing you of FOC. Ideally, you want to find the weakest shaft that will work well for the broadhead weight and bow draw weight, etc. That way you can max out FOC by concentrating as much of the weight forward as possible.
 
Over and under spined arrows will affect flight of the arrow. an over spined arrow will not fly as well as a properly spined one.
I suggest using this site to find the best arrow for your setup. Adjust arrow length, broadhead weight etc until you find the optimum combo

Archers advantage online
 
Here’s an example of how a little extra spine makes a BIG difference. I’m shooting 225 grains up front, 29” draw and arrow at 54lbs. Started with a 340 spine. Good groups. Experimented with 300 spines and could not tune the bow to shoot them as good as the 340’s. The calculators suggest 300-350 spines
 
I may be going against what a few of you have found from your testing but a properly tuned compound bow can handle overly stiff spine shafts.
Traditional bows can not.
If you are underspined you'll have issues with every bow but in my 40 years shooting bows I've never had an issue getting 250 spine arrows to hit behind the pin no matter what point or insert weight I had up front.
 
I may be going against what a few of you have found from your testing but a properly tuned compound bow can handle overly stiff spine shafts.
Traditional bows can not.
If you are underspined you'll have issues with every bow but in my 40 years shooting bows I've never had an issue getting 250 spine arrows to hit behind the pin no matter what point or insert weight I had up front.
I think with compounds you can get a way with a lot.. over spined arrows, cam lean, various other improper tuning.. but in the end, is it the "best" you can do, when having an overly spined arrow? no.. But is it good enough? will it kill a deer? sure.
 
I think with compounds you can get a way with a lot.. over spined arrows, cam lean, various other improper tuning.. but in the end, is it the "best" you can do, when having an overly spined arrow? no.. But is it good enough? will it kill a deer? sure.

As it relates to hunting, I've seen a bunch of animals killed with all different types of arrow configurations. I don't think there's a perfect combo.

What everyone is looking for is decent weight and good arrow flight. From the onset of my quest to figuring it out from trial and error I learned a stiffer shaft was more durable and with that durability came a more efficient stick.
Basically, a stiffer spine arrow shoots and tunes just fine out of all the set ups I've owned. I get them to bareshaft and paper tune without issues. My bow is also perfectly tuned and my data comes from shooting 430-675 grain total weight arrows.

A heavier spine arrow has less flex on contact with an animal too and what I see while shooting a 70 pound bow is a reduction of the arrow buckling from nock to point and most of the initial transverse oscillation will still be present, if aerodynamic damping can be neglected and that's what you gain from a stiffer spine shaft.

All I'm saying is from what I've seen they penetrate well and are more durable than a borderline underspined shafts.
 
On the face of it, you could probably beef up the insert weight and your point weight to get that monster to flex but at what cost in terms of trajectory? If you’re a shorter draw archer than it’s going to conflate things even more. Can it be done? Most likely. Should it be? I wouldn’t do it but that’s me. You need to do what makes you feel like you’re more effective.
 
I may be going against what a few of you have found from your testing but a properly tuned compound bow can handle overly stiff spine shafts.
Traditional bows can not.
If you are underspined you'll have issues with every bow but in my 40 years shooting bows I've never had an issue getting 250 spine arrows to hit behind the pin no matter what point or insert weight I had up front.

That’s a fact.

If you can’t tune a spine that’s too stiff, something else is wrong.


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