260 or 300 spine for my setup?

[Pelagic]

I've been going back and forth on these and wanted to throw it out there for some feedback before I put the order in. Here's the info:

- 68lb draw
- 30" arrow length
- arrow speed approx. 280 fps

I'm probably going with an Iron Will solid 125 grain broadhead, along with their 25 grain hit insert and 25 grain impact collar. So 175 grains up front.

What spine would you go with? I'm leaning toward .260 as I've read it is harder to over spine than under, but wanted to get some feedback based on the specifics above.

 

[Topo_trekker]

260. It will be easier to add point weight if need be.


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[doncarpenter]

I've been going back and forth on these and wanted to throw it out there for some feedback before I put the order in. Here's the info:

- 68lb draw
- 30" arrow length
- arrow speed approx. 280 fps

I'm probably going with an Iron Will solid 125 grain broadhead, along with their 25 grain hit insert and 25 grain impact collar. So 175 grains up front.

What spine would you go with? I'm leaning toward .260 as I've read it is harder to over spine than under, but wanted to get some feedback based on the specifics above.

Give me some more info and I will run the numbers.

Draw length
Bow specs ibo rating
Brace height
Axle to axle

Fletching #
What kind
How long
Weight of vanes
Wraps? Weight?
Standard nock or lighted?

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[Trial153]

30 shaft 175 grains up front .....260s

 

[Pelagic]

Thanks Don.

Draw length - 29"
Bow specs ibo rating - 325
Brace height - 7"
Axle to axle - 34"

Fletching # - 3
What kind - Blazer
How long - 2 inch
Weight of vanes - 18 grains (6 each)
Wraps? Weight? - no wraps
Standard nock or lighted? - lighted

 

[doncarpenter]

Thanks Don.

Draw length - 29"
Bow specs ibo rating - 325
Brace height - 7"
Axle to axle - 34"

Fletching # - 3
What kind - Blazer
How long - 2 inch
Weight of vanes - 18 grains (6 each)
Wraps? Weight? - no wraps
Standard nock or lighted? - lighted

So, I assumed you are going with Easton Axis since you were talking about HIT inserts. If you are looking at a different arrow let me know. I am also assuming you are using a nockturnal which weigh 20 grains. Here is what I came up with.

Just keep in mind that these are just estimates of how the spine will react. Actual shooting may show different results.

If you went with 300 and they were giving you a weak reaction you could always cut an inch or more off the shaft at your draw length and still have good clearance.

Is there are reason you want a 30 inch arrow?

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[doncarpenter]

Also given the specs you provided you are pretty far off from the 280 fps just based off the calculations. Maybe you want to use a lighter gpi arrow?

 

[doverpack12]

I shoot pretty close to the same but 80 pound 330 Ibo bow at 29.5”. I use 300 spine Easton axis arrows cut 27” carbon to carbon with a 60 grain insert and the 16 grain aluminum hit behind it and 100 gr boradheads. 3 max stealth and bohning a nocks. Right at 500 grains doing a confirmed 282 fps. I certainly wouldn’t think you need 260s with 12 pounds less draw and 3 extra inches of arrow. Mine shoot bullets as bareshafts and shoot Broadheads great. Bareshafts with field points consistently. I don’t think they would shoot like they do if they were underspined.

 

[Pelagic]

Thanks, Don. Yes - Easton Axis + Nocturnal

Is there are reason you want a 30 inch arrow?

No reason, that is just the length I have been using, but I could probably go an inch shorter.

So based on the calcs you ran, that software looks to be suggesting .300 spine as the way to go. Am I reading that right?

Also given the specs you provided you are pretty far off from the 280 fps just based off the calculations. Maybe you want to use a lighter gpi arrow?

Yeah it's surprising that those results are showing much lower speeds. I chrono'd at 280-282 pretty consistent, but that was with a setup of Easton axis .340, and 100 grain broadhead + standard insert at the front. Everything else the same. Can adding that much weight up front really reduce speeds that much?

 

[doncarpenter]

Pelagic, I know we talked already but here are the numbers with 340 spine. You're right there with the 280 speed you were getting but there is a 108 grain difference between the two arrow spines, which is significant.

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