Spine?

[87TT]

I am probably over thinking this but maybe one of the gurus here can help me out. I am wondering if my spine is correct. My arrows are Gold Tip Hunter Pro 300 spine. I have a 50 grain insert and 125 gr heads. The arrows are 30.5 inches and I am shooting a 70 lb Hoyt Pro Defiant. I can;t seem to get an answer from the charts and calculators I have found.

 

[OR Archer]

What’s the draw length of the bow?

 

[Rob5589]

Guessing a draw length of 30", you are on the edge of under spined.

 

[Page Master]

Guessing a draw length of 30", you are on the edge of under spined.

I would think so too. If you are drawing that long and want to keep 30'' of arrow, you will probably need 250's. If you already have a dozen of the 300's, try to cut as much off as you can while leaving at least 1/8'' of arrow past the rest. Try by cutting off 1/8'' at a time, give or take and testing from there.

 

[Billy Goat]

I know the defiant turbo was hard on spine, I'm not certain with the pro.

Are you seeing anything indicating weak spine?

I don't see any disadvantage to going to a heavier spine, makes everything easier.

 

[87TT]

Yeah, real close to 30 inch draw. 300 is the stiffest they make unless I totally change arrow type. I may have to back off the Draw weight a turn. At least for this year.

 

[brettdunn7]

I am shooting Victory RIP TKO 250s at 29.25” length 100gr insert and 125 gr head. 29” draw length at 75# if that gives you any idea.


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[87TT]

If you look at the charts, I'm ok but they don't take in the 50 gr insert. I just now added a few twists to the string and dropped the draw length back to 29.5, where it always was and should be. other then a loss in speed and lower hits on the target, I am grouping way better. I also took off the limb stop to press it and haven't put it back on. I may still take a half turn off the limbs. I could feel myself getting a little tired so I stopped for now. Plus it's getting hot. Was 109 yesterday.

 

[Billy Goat]

Think your supposed to add 3# draw weight for every additional 25 grains on the front of the arrow.

For example:

125 grain head with 50 grain insert, add 6# if the chart has 125 grain head, add 9# to draw weight if it's for 100 grain heads.

 

[87TT]

If I can't get it to work to my satisfaction, I may experiment with 100 gr heads. would make my arrow weight about 474 instead of 499.

 

[Yooper]

Do you have any tuning or flight issues that you're trying to solve? That will be a better indicator than any charts/graphs.

 

[87TT]

I think a lot of my issue is mental at this point. The other day I shot pretty good with the 499 gr arrow and the 30 inch draw length. But not as constant as L liked. I've been measured and always shot at 29.5 inch Draw. Sometimes everything feels right but my group would open up at longer ranges.. I used to shoot 5 arrows at 100 yards every day at a Rinehart 18-1. Would get 5 or 4 out of 5 constantly. Then the new string and longer draw length. Timing is good. Draw length is back to 29.5. I have some 100 gr FPs on now and am going to shoot them for a day or so and see. I think a lot of my problem is less than two weeks until elk season. I just never though about the added weight of the inserts affecting the spine. Now it's in my head messing with it.

 

[Yooper]

Have you done any bare shaft tuning? You should uncover any kind of tuning/spine issues with some bare shafts and fletched at 20 yards. Might give you peace of mind as well.

 

[aachey]

I could be wrong, but I thought I've heard of people lowering draw weight to check arrow spine. I'm assuming you want to keep your arrow and bow specs where they are at, but it could be a quick and easy check to see if it shoots better without yard sailing the whole thing.

 

[87TT]

Good idea.

 

[87TT]

Have you done any bare shaft tuning? You should uncover any kind of tuning/spine issues with some bare shafts and fletched at 20 yards. Might give you peace of mind as well.

Good idea.

I could be wrong, but I thought I've heard of people lowing draw weight to check arrow spine. I'm assuming you want to keep your arrow and bow specs where they are at, but it could be a quick and easy check to see if it shoots better without yard sailing the whole thing.

I am currently going to shoot some 100 gr FPs to see if it makes a difference. Both shoot good through paper.

 

[isItFallYet]

After reading your post, I too, did some more research since I was recommended a 340 spine. Per every arrow spine calculator that I have researched, it looks like my spine deflection should be much lower.

The Easton calculator seems to be the most confusing.

From the Easton website: (https://eastonarchery.com/huntingshaftselector/)

1. Determine your correct arrow length per diagram above.
2. Determine correct peak bow weight (not holding weight) and draw length with the assistance of a qualified archery pro shop.
3. Determine the ATA (Archery Trade Association) rating velocity of your bow.
4. Factor variables to the “standard compound setup” to determine CALCULATED bow weight. For compounds the “standard setup” includes use of a release aid and a brace height greater than 6.5”. Deviations for the standard compound setup require factoring in EACH VARIABLE as follows:
A. Brace height lower than 6.5”- add 5 lbs to CALCULATED bow weight.
B. Finger release- add 5 lbs to CALCULATED bow weight. Add the total of actual PEAK bow weight and all CALCULATED bow weight adjustments to determine final calculated weight. For example, with a 60 lb peak bow with a 6” brace height, calculated bow weight will be 60+5 for a calculated 65 lb bow weight. Now, in the “Calculated Peak Bow Weight” chart, select the column under the ATA range for your specific bow and your point weight. Follow the column down to your CALCULATED bow weight. Then, follow the chart to the right until you reach the column with your correct arrow length, and note the group letter (A-M). This letter will represent the suggested arrow group for your selection.

I'm shooting a Mathews Vertix set at 70lbs and ATA rating velocity (or IBO) of 343 fps. So add 5lbs since it's over 340 IBO, which now = 75lbs

Also add another 5lbs since the brace height is less than 6.5", so add another 5lbs, which now =80lbs

Again, add another 5lbs since I'm using a finger release. That gets to 85lbs.

So going off of Easton's charts and their calculator, there isn't an arrow that fits the math.

Am I doing something wrong? If so, what am I screwing up? Either way, I have been shooting 340 Axis arrows and that is what I plan on flinging at an elk if I get the opportunity.

 

[Marble]

All of those numbers are approximate. So just keep that in mind. Shortening arrows stiffens them up, sometimes its enough, sometimes it is not.

Just IME, I error on the side if stiff. I'm not sure how long your arrow is, but there is an arrow that will work for you. If you have the standard 70 lbs bow between 28 and 29.5 inches, there are tons of choices. Lower the poundage,,,even more. Your bow seems to be within the realm of very normal. So you might be overthinking it.

Arrows can and are usually much shorter than your draw length. So if you have a 29 inch draw, arrows can be anywhere from just over 27" to as long as you want. Kind of depends on where your rest sits.

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[isItFallYet]

My arrow is 30”

 

[Brendan]

My arrow is 30”

What's your draw length?