Spine help?

[PredatoronthePrairie]

Hoping someone can help out.

Been shooting a new bow that I bought from my longtime archery guy. Starting to question a few things. But that is a story for a differnt day.

Hoyt ultra8 70limbs 30in draw about 68# DW. Clocking around 283fps

He said I should be fine slinging the same arrows as my old setup. Have been pretty dialed practing out to 80. Till I went to papertune and shoot broadheads. Noticed I am getting a wicked right tear. That I can't tune out.

Had been shooting Easton axis 340. Standard insert weight. No add on. 4 fletch

Right around 450grain total.

Im thinking need to bump down to a 300 or maybe even a 250 spine.

Any insite appreciated. Can provide more info if needed. Thz

 

[Bump79]

If they are shooting fine don't sweat it. I used had the exact same setup at 30" 70# and the same exact 340 Axis and had the same problems. A 300 spine arrow fixed it up really well and that's where I've been for 5 years. 250 would work but isn't needed.

Let me know if you need some built.

 

[Mighty Mouse]

You're probably on the weak side of what spine charts/calculators would recommend, but more info is needed to better evaluate spine:

• Carbon-to-carbon arrow length?
• Field point/broadhead weight?
• Insert weight? 25 gr half-out and 16 gr HIT (shown below) are commonly used with a 5mm Axis, but there are many other insert options

Before making any adjustments based on a paper tear, I would recommend confirming the tear with multiple arrows at multiple distances from the paper. If there's a consistent nock right tear, move the rest to the left and/or shim the cams to the right.

 

[Billy Goat]

At 30" DL I don't think you can get a 340 shaft short enough to be where I'd want to be spinewise for a hunting arrow.


I'd step upto 300 spine, if arrows are past 30" in length go to a 250

 

[Skerhunter]

340s are getting weak past 27-28” @ 70lbs. 300s are getting weak at 29/30” and 70lbs. I have better luck tuning going with the stiffer option…

 

[bergie]

As folks have correctly said before, if in doubt err on the stiffer side.

For a total arrow weight of 450gr there can't be a ton of weight up front while shooting the axis (probably 125gr head and 16gr insert) so assuming nothing will change but the arrow, a 250 spine is probably not needed, but I would definitely bump up to 300.

 

[PredatoronthePrairie]

Thz everyone.

Additional info
Believe the inserts are the 16g HIT. For 5mm axis 340

And shooting 100grain points.

 

[Bump79]

Thz everyone.

Additional info
Believe the inserts are the 16g HIT. For 5mm axis 340

And shooting 100grain points.

Yep. I had the same exact arrow setup and draw length/weight. Go 300's. I can run 175 grains up front on a 300 and have amazing flight. 250's were fine too but I liked the weight of the 300's.

The 340's will fly fine for practice with field points. I'd get another 204 shaft in 300 spine and get the total arrow weight the same, if you need help we can get ya there. Then you'll not be out shafts.

 

[Mighty Mouse]

If you cut a 340 at 28" carbon-to-carbon with 116 gr on the front and 35-40 gr on the rear, you would be real close to "optimal" spine per Pinwheel. 300 is still probably a better choice, but you may be able to get a 340 to work if you trim it down.

 

[PredatoronthePrairie]

Hate to bring this back up. But I'm at a loss of words and frustrated.

Took the bow back to my archery shop.

Put on a new string. Got everything squared away timing wise. Shimmed the cams to try and get rid of the tear.

Thought we had it figured out.

Broadheads are still consistently hitting high left.

I've tried moving rest down and left.

And rest down and right. Both don't bring the arrow in.

Have tried differnt broad styles, and point weight. Nothing.

I still think it may be arrow spine related.

But all the tuning guides and the shop say that is not the issue.

Any last ideas on what the problem might be?

Looking like I will be taking the backup bow on my trip. Only got 8 days to figure this out.

 

[H@mstar19x3]

Hate to bring this back up. But I'm at a loss of words and frustrated.

Took the bow back to my archery shop.

Put on a new string. Got everything squared away timing wise. Shimmed the cams to try and get rid of the tear.

Thought we had it figured out.

Broadheads are still consistently hitting high left.

I've tried moving rest down and left.

And rest down and right. Both don't bring the arrow in.

Have tried differnt broad styles, and point weight. Nothing.

I still think it may be arrow spine related.

But all the tuning guides and the shop say that is not the issue.

Any last ideas on what the problem might be?

Looking like I will be taking the backup bow on my trip. Only got 8 days to figure this out.

Did you change arrows?

 

[PredatoronthePrairie]

Not at this point. Cause my archery tech guy has been adimant that was not the issue due to where the arrows are impacting. He was telling me that I was to stiff according to the charts which I told him was impossible.

30.25" carbon to carbon.

Bow set st 30in draw.
70#

Now trying to figure out between 260 and 300 leaning towards 300. But am only gunna have one chance to get this right before time is up.

 

[H@mstar19x3]

Not at this point. Cause my archery tech guy has been adimant that was not the issue due to where the arrows are impacting. He was telling me that I was to stiff according to the charts which I told him was impossible.

30.25" carbon to carbon.

Bow set st 30in draw.
70#

Now trying to figure out between 260 and 300 leaning towards 300. But am only gunna have one chance to get this right before time is up.

I'd try and buy 2 250 and 2 300 spine arrows. get them cut and set up. shoot and see which is better. your tech is wrong. you are underspined which makes me wonder about the rest of his work to fix the issues.

 

[OH->CO]

I have been down a similar route before. I had a guy that owned the archery shop say that he isn't religious about paper tuning, although its nice to be close. My broadheads dont hit where my field points do so I just shoot broadheads only for a while before season. I dont spend my time worrying about field points. If I wanted to get them closer then I would go to a stiffer spine. I shoot 70lbs and 30" draw with 32" arrows. I currently shoot 300 spine and it is not stiff enough. I should be going to 250 or 260

 

[Hussar]

The results speak for themselves. You aren't getting good broadhead flight, no matter how much adjustment you make. It doesn't matter what anyone else says.

I'd say the safest bet would be to get the 250/260 spine arrows. It's better to be overspined on a compound bow than underspined. I don't think you'd have issues with the 300 spines, but like you said, you don't have the time to run through testing to make sure.

FWIW: I'm shooting 75lbs/28.5" and using a 300 spine with 175 grains up front. 300 spine arrows tune just fine for me. I also have some 250 spine arrows and they will group with my 300 spine arrows at 40 yards.

 

[Mighty Mouse]

my archery tech guy has been adimant that was not the issue due to where the arrows are impacting. He was telling me that I was to stiff according to the charts which I told him was impossible.

Your archery tech is mistaken. The old "left tear = arrow is too weak, right tear = arrow is too stiff" (for a right-handed shooter) adage is a holdover from traditional bows shot with fingers that doesn't apply to modern compound bows shot with a mechanical release. With a modern compound setup, the arrow doesn't have to bend around the riser and nock travel isn't influenced by fingers on the string, so there's nothing predisposing an overly weak or stiff arrow to leave a compound bow flying one way or the other. Arrow spine can affect how a compound bow tunes, but the effect doesn't necessarily manifest as "left tear = weak, right tear = stiff".

A 30.25" 340 shaft is quite a bit weak at your specs per the spine charts/calculators. Trimming a 340 as short as possible may stiffen it enough to get good broadhead flight, but switching to 300 spine would be a better solution.