Under spined?

[old_coyote]

Just got a dozen new arrows from a reputable bow shop and looked at the chart and I think they are incorrect... am I crazy? With the added 40g I think I need 300’s

Mathews VXR 31.5
70# 29” mods << don’t know actual #

Gold Tip Hunter Pro 340

• 8.9 gpi
• Straightness Tolerance: +/- .001"
• Weight Tolerance: +/- .5 gr

2" blazer vanes; 3-fletch

27-5/16" carbon to carbon

~152.2 arrow weight

~437g full arrow weight including 40g in each

100g field points

FOC = 13.7%

 

[Sled]

everything i've read about that bow says they like weak arrows. shoot it then decide.

and after looking at your setup, those don't look too weak. 340 seems correct for that weight and DL. your foc isn't crazy either.

 

[old_coyote]

Thanks sled; am I reading this chart wrong?
With the extra 40g up front I think I am way off...

I’ll give it the ol college try and see but am curious

 

[Sled]

i wouldn't get too hung up on the chart. they are a guide line to start from but ultimately it comes down to the bow and how you shoot it. it's nice to have a few different bare shafts around to see what the bow likes before purchasing. don't forget to turn your nocks before giving up on a certain spine or shaft.

 

[Mighty Mouse]

340 is borderline weak per the charts if you're adding weight beyond the "standard" front end configuration of 100 gr point with 12 gr aluminum insert, but I bet you can still get them to fly well. If you're stuck with them now, might as well give them a try. If you have difficulty tuning the 340's and suspect weak spine is the root cause, you could reduce your draw weight or reduce your point weight.

Also, if the component weights and TAW you listed are correct, you must have some extra weight on the back end, which stiffens an arrow's dynamic spine. 243 gr shaft + 100 gr point + 40 gr insert + 18 gr fletching = 401 gr, which is 36 gr shy of your stated total weight. I could see a lighted nock plus a wrap weighing 36 gr combined, but I doubt you'd be getting 13.7% FOC if you truly do have that much extra weight on the back.

 

[old_coyote]

Thanks! I’ll double check a few things. No lighted nock or wraps.

The extra weights I have up front thread onto back of standard insert and have the nock+GT collar thing.

 

[Billy Goat]

I'm shooting a setup pretty close to the same. Except I'm 65# with the 340's, standard insert and 125 grain head. I'm right on the edge I believe. These bows push an arrow pretty hard. Mine tunes, but I wouldn't be trying to use a 340 @ 70#.

That said if it's the gold tip aluminum insert, it's pretty long. They stiffen your arrow a bit from how much space they take up in the front.

I doubt you are returning them. Give them a try. You can start backing poundage off to get them to work, tho I'm sure you don't want to do that.

 

[gelton]

Here is what your setup looks like on Archers Advantage (its only like $12 year to sign up):

 

[old_coyote]

Thank you gelton

 

[gelton]

Thank you gelton

Actually, I just noticed that I kept my DL instead of yous (28.5 vs 29) and with a 29DL it says too weak....however as others said, you could probably back off the poundage a lb or 2 and be okay. 67lbs will get you back to marginally week, at least according to AA.

 

[Samdemarais]

I would shoot them and see how they fly with broadheads. If they are not hitting with tips you can try taking a turn or 2 out of your limb bolts to get them to tune or take a little more off your arrow.

 

[old_coyote]

Thanks all. I have a feeling the bow shop would not be much help if I went in and asked why they sold me improperly spined arrows...

 

[Steve1662]

Playing around yesterday I bumped my field point weight up from 100 to 125. Expected the arrows to hit low but they were consistently hitting everywhere. Based on the charts the added 25 up front would put me boarder line under spined. The further distance I shot at the better they flew/grouped though. Groups were normal at 60 yards and tighter then what I could get at 20. I assume the point weight is too much for the intial inertia but the arrow is able to stabilize itself the longer it is in flight. Anyone else experience this?

Sent from my SM-G950U using Tapatalk

 

[Billy Goat]

Playing around yesterday I bumped my field point weight up from 100 to 125. Expected the arrows to hit low but they were consistently hitting everywhere. Based on the charts the added 25 up front would put me boarder line under spined. The further distance I shot at the better they flew/grouped though. Groups were normal at 60 yards and tighter then what I could get at 20. I assume the point weight is too much for the intial inertia but the arrow is able to stabilize itself the longer it is in flight. Anyone else experience this?

Sent from my SM-G950U using Tapatalk

A weaker spine generally flies better at distance. It's more forgiving. Problem is when you put a broadhead on the front getting them to hit correctly.

Before you sell yourself on switching to a heavier head, make sure you play with broadheads.

This is from Easton tuning guide:

 

[Steve1662]

A weaker spine generally flies better at distance. It's more forgiving. Problem is when you put a broadhead on the front getting them to hit correctly.

Before you sell yourself on switching to a heavier head, make sure you play with broadheads.

This is from Easton tuning guide:
View attachment 293413

View attachment 293414

That explanation on figure 18 makes total sense. And thanks for sharing that Easton tuning guide. Can only imagine there is a wealth of knowledge in there and will definitely give that a read.

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[old_coyote]

Thanks all. I have a feeling the bow shop would not be much help if I went in and asked why they sold me improperly spined arrows...

I woke up with a new perspective; you know who’s fault it is that I spent $230 on potentially incorrect arrows? Mine.

I should be better, know more, become a subject matter expert and have started bow tuning and arrow building a long time ago.

$230 lesson in discipline and a free kick in the pants!

happy Sunday ya’ll

 

[Mighty Mouse]

I woke up with a new perspective; you know who’s fault it is that I spent $230 on potentially incorrect arrows? Mine.

I should be better, know more, become a subject matter expert and have started bow tuning and arrow building a long time ago.

$230 lesson in discipline and a free kick in the pants!

happy Sunday ya’ll

Good attitude to take. I've been there before too lamenting money spent poorly due to my own ignorance.

You may yet find that those arrows will work for you, especially if you're willing to remove some of the FACT weights or trim the arrows down a bit more (although you may already be close to the minimum length needed to keep the arrow on the rest).