There is no such thing as an overly stiff spine with a compound bow. With a recurve, a stiff spine is problematic, but not with a compound bow. The only exception would be an arrow released with fingers instead of a mechanical release aid, from a compound bow. The less oscillation and flex you have in an arrow the better, but with an arrow released with fingers, the string's path is not straight, as it is with a mechanical release aid. Therefore; the arrow requires the ability to flex laterally to maintain the intended path to the target. You will read in some tuning instructions that weak arrows impact left and stiff arrows impact right for right handed shooters ... this is true with finger shooters only, and for the reasons explained above.

Consider this. Where is the spine indexed and the index vane placed for compound bows? Either on the top or the bottom. On a fingers-released setup, it will be to the left or right, depending on the shooters dominant hand.

On a tuned compound bow, the nock travel should be zero from full draw to brace. This means there should be no oscillation in the path of travel of the nock as it moves from full draw to brace. When zero nock travel exists, the force of the draw weight of the bow is directly centered behind the nock of the arrow. The more flex you have in the arrow, the greater margin of error. A stiffer arrow will follows it's path more consistently, as the vanes on the arrow have less correction to make due to less oscillation of the arrow.

The only benefit you will achieve in choosing the weaker of spine choices is a lighter arrow shaft. If that's what you're after that's perfectly fine. But there is really no need to think too deeply between 300 and 340, otherwise - choose 300.

With a fixed blade broadhead, the shaft that flexes more than another will experience grater competition between the broadhead steering the arrow, and the vanes steering the arrow. Think about how an arrow flexes as it's released.

 

There is no such thing as an overly stiff spine with a compound bow.
….

Mike nailed it. Centershot compounds shoot and tune well with overspined arrows- period.

The danger is when you are close to being under spined with broadheads- a big NO No.

PLUS, the heavier spine gives you a more durable arrow and I’ve seen better penetration- less flex.

 

I would do the 300 because down the road you may want to add more insert weight, I shoot 340 with 100 grain insert and 100 grain broadheads, I shoot 50 lbs at 29 inch draw..
Lucky

 

with those specs with a 340 IBO bow I would go 350, if the extra weight is an issue
you can go with a lighter weight 5mm 350 like a BE Rampage or GT Black Labels which are 8.2gpi to the Axis 9.5gpi

 

.340 spine all day with your specs. I'm shooting a V3X29 at 66.5lbs and 28" 80% draw mods with a 27.25" carbon to carbon .350 spine Victory RIP TKO 451 grain TAW. Bareshafts are lasers and every fixed broadhead I have tested is money out to 80 yards. Do not buy into the theory that you need to overspine your arrow selection with every bow!! The Switchweight Mathews bows are very spine tolerant! Good luck!

NC

Sent from my SM-G970U using Tapatalk

 

340 is probably a better match for your specs right now. If you add any more weight to the front you will probably need a 300 though. All depends on how locked in to that build you are.

 

Thanks everyone for your replies!

@NCAVI8TOR your bow setup sounds almost identical to mine! The shop I bought from recommended 340/350 spines as well, which is why I was caught a bit off guard when Iron Will recommend the 300s.

I'm fairly locked in to the setup. It's going to be 80% whitetail, and I like the benefits of a 125gr broadhead, but don't feel the need to get crazy with weight on the insert and collar, maybe could go up 10-20 gr. max. I want to balance speed and terminal energy. @BlackSunshyne how much more weight would push you to a 300 in your opinion?

A 340 shaft with my build would be around 450gr., with the 300 it's around 490gr. I do think 490 is a bit on the heavy side for my taste so I am leaning towards the 340s. 450gr is an ideal balance between speed and terminal velocity imo.

 

Thanks everyone for your replies!

@NCAVI8TOR your bow setup sounds almost identical to mine! The shop I bought from recommended 340/350 spines as well, which is why I was caught a bit off guard when Iron Will recommend the 300s.

That is because either will work and they know that it's more about preference. The 340 is probably the better "fit" if you are a slave to the charts and use more "normal" point weights but many of us know it's hard to over-spine a modern compound. So if you went with the 300 it would tune up fine as well (just like the 340's) and you'd have more options on point weight than with the 340's. If that even matters to ya'.

 

The deal with the Axis is its a heavy per inch shaft relatively. I would go with a .300 spine myself, and a lighter per inch shaft, it will be more versatile, allow you to add a heavier broadhead later if you wanted. I would probably use the Victory standard RIP arrow. Its .204 same as the axis. It comes with a 60 grain stainless steel outsert. I would screw that IW broadhead right on that. The number I ran using your info but the Rip specs at .300 spine came out
Your approx. arrow weight is: 462.1 grains.
Your arrow FOC is: 14.2%.

I shoot .340's out of 50 lbs all the time. See you go .300 then you want to go shoot something really big, you could just add like a 150 or 175 grain broadhead and push the weight up to 500 grains and it would be higher foc and the whole deal. I do this a lot with my arrows, allows me to just change heads, re -sight, and change from a lighter to heavier setup at will.

 

The deal with the Axis is its a heavy per inch shaft relatively. I would go with a .300 spine myself, and a lighter per inch shaft, it will be more versatile, allow you to add a heavier broadhead later if you wanted.

That's what I have evolved to over the years "if" I shoot carbon. If you go a tad on the stiff side and pick a light GPI you can shoot light arrows for 3D or hunting if that's your thing.

Or you can add point weight, lighted nocks, wraps or whatever and still not be too heavy for a hunting arrow. Or you can add point weight and get higher FOC without shooting a 480+ grain arrow. Or weighted inserts. They are a lot more versatile for sure.

Also the stiffer arrow will tune up fine with less point weight it just might be less forgiving of tuning errors. If you go with he heavier points it'll just tune up easier. But the point is you can do it all with a stiffer arrow.............you can't if you pick the arrow that's perfect for your setup.....it'll get too weak if you try.

Remember when BIG fat line cutters came out they were all 250 or 300 spine and people were shooting them at 60 pounds or less in 3D all the time..............lol

I'm doing the same thing now....I could shoot 400's but I'm shooting 340's and have some wiggle room to play with. In the past at #65 I have shot 300's and done the same thing.

 

When in doubt I always go heavier spine

 

Your right where either one could possibly tune well. The best way to determine would be to shoot a sample of each at distance. I have found at yardages 50 and above really tells allot about correct spine through arrow grouping, both with weak and overspined arrows. If this is not possible and you need to pick just one, then with your setup I would go .340.

 

I’m in the same boat. Shooting an E35 at 28” 62lb with 150-250gr up front. All the charts tell me 350, but when asked everyone told me 300.
This was my bareshaft at 40yrds with a 350 and 200gr up front

 

NICE....how do they shoot at 60yrds?

 

Following

 

If you want options, go heavier spine. Never had an issue with over-spine, but had trouble shooting heavier heads on the .340's.

 

I am shooting the same bow with 65lb mod coming in at about 67 lbs on the scale. draw is 28.5 and my total arrow length is 28. I went with 300 and its tuned just fine and I'm using 100 gn broads so with 125 you should be good with 300. I think you can go either way and make it work.

 

300!

 

 

I literally just spent 4hrs shooting with broadheads 150gr, V3X 28inch @70lbs 472 arrow weight and tuning all of my Axis 5mm 340 arrows at 40yds. I was writing everything down where each arrow landed and after I started seeing patterns I would move my rest accordingly. Then I would take my fliers anything greater than 4" @ 40yds and move the broadhead to a different arrow until I was close. I then started nock tuning 1/16 of a turn to bring the broadheads to 2-3 inches at 40yds. I was using lighted nocks so I could see when an arrow didn't fly perfect. I still think that after all this work I'm likely 1.5" lower on average than my broadheads than field points. My should is burnt so going to leave everything where it is right now. I have seen a few times where I will move the rest and field points literally stack on top of each other but then broad heads hit 3" low left. I then move the rest and the broad heads group with field points but slightly larger groups still 4" or less. This seems to go along with this article. With all this I am going to build 1 Rip TKO at 300 and see how sensitive the arrow is to changes in nock position.

New Insight on Arrow Spine - Bowhunter

Get "weaker" and improve your accuracy.

www.bowhunter.com

 

I would like to know;

Where does the DATA come from to develop that software?

My bet is its from the old arrow charts we have used forever...and its less relevant today with shoot through risers.

 

I would like to know;

Where does the DATA come from to develop that software?

My bet is its from the old arrow charts we have used forever...and its less relevant today with shoot through risers.

People have to load it in, right? I still get a laugh out of people that go to the computer to fine tune and crunch all the numbers and then you STILL only have a few choices..........lol. Most of us are going to fall in the 400, 340/350 to 300 range....but putting all that in the computer feels good I guess?

Very few will stray outside that to the 250 or 500 choices but still you only have 5 options in reality.........

In time if you go to the charts you pick the right spine and if you vary the point weight you can easily compensate for it with experience. The other option (like overusing a GPS) is to forget thinking and let the machine do all the thinking for you.