Arrow spine EMERGENCY-SOLVED

North

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I leave for Montana (elk) in less than two weeks and I’m dealing with a major archery crisis :( Hopefully someone with a better understanding of this stuff can weigh in as to what I should do.

My bow is an Elite Energy 35 64 lbs 30” draw 330 ibo
Iron Will 125g broadheads
FMJ 5mm 30” arrows

I had been shooting the 340 spine FMJs because that’s what the shop told me I needed. I got some Iron Will 25g outserts so I recalculated my recommended spine and the chart says 300 or lower. So I ordered a dozen 300 spine and when I went to redo my sight tape for the heavier arrows I’m only getting an estimated 245 FPS which is the lowest speed sight tape that comes with the sight.

That is a little embarrassing.

My bow was never fast (265ish) but when using the suggested spine I lose FOC and the arrows weigh 555 grains (old arrow was 494 without the outsert). The next FMJ spine down is slightly lower GPI but not enough to make a big difference. Even if I drop the outsert I’m still not at 340 spine on the chart.

Is it sort of weird that with a 330 ibo bow at 64 lbs and 30” draw that I’m shooting that slow with the recommended spine?

Both the 300 and 340 seem to be shooting well for me. Guess my options are:

-go with the 300 spine and hope the elk is asleep
-Go with the 340 and be spiritually bothered by shooting the wrong spine, and possibly have flight issues
-buy a faster bow with less than 2 weeks to set it up and practice with it
-a new arrow?
-die

help please
 

danwattsmessick

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How did your original 340 spine arrows fly? What made you switch?

What is the concern with the 340s? Safety?

Edited to add; This is the main reason I dislike FMJ arrows. They have a high GPI which makes it difficult to build a stiffer arrow with a higher FOC without ending up with a significantly heavier arrow overall.

In my opinion you'd be better served finding an arrow in the correct spine but with a lower GPI so that you can build the arrow with the components you like and end up with an overall total arrow weight you're happy with.
 

ncavi8tor

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Your worry over speed is unnecessary and why is it "embarrassing?" A 555 grain arrow at 245fps is a very good setup! That is 74 ft/lbs of KE and .60 slug/ft per sec. of momentum!

If the .340 spine is shooting good with your chosen broadhead out to your max range I wouldn't change anything this close to season. That is also a good arrow setup.

I also do NOT like FMJs for the same reason as the above poster and the fact that they will take a bend eventually. The Axis or Hexx are much better shafts.

One more thing: The arrow spine charts are a general guideline. There is some latitude to allow for fine tuning your custom arrow builds. Arrow/broadhead performance downrange is the ultimate spine indicator.

NC

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CougarBlue

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AZ
I'd stick with the old 340 set up if it were me and lose the outserts. 494gr is plenty enough for an elk and if they are flying well and hitting consistent out at range, then tweaking with it at this point in the game seems risky.

But I'm conservative with my setups and don't like to screw with things this close to the season. Save the tinkering for next spring.
 

N2TRKYS

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I definitely wouldn’t be happy with that speed. That sounds about right with such a heavy arrow, though. Rock on with what you’re doing and fix it when you get home.


Good luck on your trip.
 
OP
North

North

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How did your original 340 spine arrows fly? What made you switch?

What is the concern with the 340s? Safety?
I was just under the impression that underspined arrows could cause flight problems. Not really concerned with it blowing up since I’ve shot 1,000s of arrows with this setup minus the outserts.
 

danwattsmessick

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I was just under the impression that underspined arrows could cause flight problems. Not really concerned with it blowing up since I’ve shot 1,000s of arrows with this setup minus the outserts.

Unless you were getting flight problems, I would stick with your 340s. You're on the border for needing a stiffer arrow and should you decide to increase draw weight you'll definitely want something stiffer, but if they flew well with your broadheads, I wouldn't mess with a good thing.
 
OP
North

North

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Your worry over speed is unnecessary and why is it "embarrassing?" A 555 grain arrow at 245fps is a very good setup! That is 74 ft/lbs of KE and .60 slug/ft per sec. of momentum!

I was being a little hyperbolic by saying it was embarrassing, but I did find it surprising that given it’s still a relatively Ok ibo bow and I have a 30” draw that I was at the absolute lowest end of the sight tapes that MBG includes in the tape set using the proper spine. Yes I should be shooting 70 pounds but the bow was mislabeled when I bought it.
 
OP
North

North

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Thanks for all the replies, that was fast! I tend to get freaked out about these kinds of things especially right before a trip. Sounds like no matter which route I go I’ll survive my crisis, I’ll probably stick with the 340s for now, I don’t need to spend another $150 on arrows just to use my outserts.
 

gelton

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I guess it boils down to how closely you rely on your range finder, not just ranging objects to prepare for the shot but actually ranging the animal right before you shoot.

I went down the heavy arrow and FOC rabbit trail and had a long-ish shot where I did not have time to range and it was a clean miss...while there are many things to blame the miss on (me, not ranging the animal and only ranging objects while setting up, having at least a 5 or 7 pin sight instead of a 3 pin slider) I think if I had a faster arrow that I would have had a nice wall hanger of an elk.

I guess the moral to the story is - it depends, but I can tell you that I am sticking with what many people have recommended on here before...shoot an arrow that gets you as close to 275 fps as you can for elk...weight and momentum are important, but IMO flight path is even more so.
 

Mighty Mouse

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I had been shooting the 340 spine FMJs because that’s what the shop told me I needed. I got some Iron Will 25g outserts so I recalculated my recommended spine and the chart says 300 or lower. So I ordered a dozen 300 spine and when I went to redo my sight tape for the heavier arrows I’m only getting an estimated 245 FPS which is the lowest speed sight tape that comes with the sight.

That is a little embarrassing.

My bow was never fast (265ish) but when using the suggested spine I lose FOC and the arrows weigh 555 grains (old arrow was 494 without the outsert). The next FMJ spine down is slightly lower GPI but not enough to make a big difference. Even if I drop the outsert I’m still not at 340 spine on the chart.

Is it sort of weird that with a 330 ibo bow at 64 lbs and 30” draw that I’m shooting that slow with the recommended spine?
The speeds you're seeing look to be right on the money. Per Elite's advertised speeds, your bow at 30" draw length is capable of generating around 84 ft-lbs of kinetic energy at 70# draw weight and 71 ft-lbs at 60#. Interpolating between those two values, puts you at 76 ft-lbs of KE at 64# DW. Ignoring the impact of increased bow efficiency at higher arrow weights and lower string speed (vs IBO) due to peep sight/D-loop/silencers (which are minor effects and tend to offset each other) and back-calculating speed based on 76 ft-lbs of KE gives you predicted speeds of:
  • 263 fps at 494 gr arrow weight
  • 248 fps at 555 gr arrow weight

-go with the 300 spine and hope the elk is asleep
The cow in the attached photo was standing fully alert at 40 yds and staring me down as I drew. She didn't care that my 630 gr arrow was "only" flying 230 fps; she took the arrow through the heart and collapsed within 100 yds.

-Go with the 340 and be spiritually bothered by shooting the wrong spine, and possibly have flight issues
Spine charts aren't gospel, just a starting point. Broadheads grouping with field points is the ultimate goal of arrow/bow tuning. If you can achieve that with your 340's, there's no reason to change arrows in search of the "perfect" spine.

-buy a faster bow with less than 2 weeks to set it up and practice with it
-a new arrow?
Major changes like those seem like a bad idea this close to your hunt.
IMG_20180830_215415671.jpg
 
OP
North

North

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I just took it out with the 340 spines and walked back from 20-80 shooting 6 arrows every 10 yards. Everything out to 60 looked good, 70 and 80 opened up a bit but it was pretty dark out. Out of curiosity I put one of the 25g inserts on one of the arrows and I’ll be damned if it wasn’t the one that was dead in the bull almost every time. I’ll try the same thing tomorrow with the 300 spines and see if there’s any difference and then start shooting some broadheads. Also FWIW my 300 spine with this bow passed through the one bull I killed with it no problem, my main concern with the new arrows was just trying to make sure there are no mechanical limitations to my accuracy. I agree with the guys commenting that the heavier arrow has advantages, I was just kidding around saying the elk would have to be asleep:) If I had a faster bow I’d like an arrow in that 550 range but for my current one I think 500ish is the sweet spot for me between speed and momentum.
 
OP
North

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Thanks again to everyone who shared advice, good luck to all and have a safe and fun season!
 

Billy Goat

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I just took it out with the 340 spines and walked back from 20-80 shooting 6 arrows every 10 yards. Everything out to 60 looked good, 70 and 80 opened up a bit but it was pretty dark out. Out of curiosity I put one of the 25g inserts on one of the arrows and I’ll be damned if it wasn’t the one that was dead in the bull almost every time. I’ll try the same thing tomorrow with the 300 spines and see if there’s any difference and then start shooting some broadheads. Also FWIW my 300 spine with this bow passed through the one bull I killed with it no problem, my main concern with the new arrows was just trying to make sure there are no mechanical limitations to my accuracy. I agree with the guys commenting that the heavier arrow has advantages, I was just kidding around saying the elk would have to be asleep:) If I had a faster bow I’d like an arrow in that 550 range but for my current one I think 500ish is the sweet spot for me between speed and momentum.


Your walkback will be fine with a weak spine. You'll start to find answers (likely more questions) with a broadhead on the front.
 
OP
North

North

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Your walkback will be fine with a weak spine. You'll start to find answers (likely more questions) with a broadhead on the front.
I’ve been using this setup or a while and my broadheads fly with my field points just fine, but I am curious to see how they fly on the 300 spines.
 

406unltd

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There’s no reason to shoot the fmj. You can get the correct spine with lighter gpi arrow. This close to season you gotta go with the setup that tunes the best. If it’s the slow arrows then so be it. Atleast they will hit good. That speed isn’t ideal for a compound but trad guys hunt with less so it can be done.
 

jmez

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Personal preference. I shoot FMJ's because of the heavy gpi. I like heavy arrows, don't concern myself with high foc or speed. My arrows tune well and shoot well.



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Jimbob

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Broadhead accuracy is WAY more important than speed. You need to shoot the 340s with broadheads and see if they have any issues. If the 340s are shooting great with broadheads then you have an awesome set-up to go hunting. If the 340s give you bad flight with broadheads then try the 300s.

A slow-flying ACCURATE arrow is much better than a faster arrow with erratic flight.


In the future, if you want your arrow to hit certain parameters (speed, weight, FOC) then you have to build them from the ground up. I search a bunch of different manufactures and models and pick the arrow that will spine right for my set-up and has the specs I want. Like guys mentioned above, the FMJ is a heavy arrow so getting the speed and foc you want in the correct spine is difficult.
 

Jimbob

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Personal preference. I shoot FMJ's because of the heavy gpi. I like heavy arrows, don't concern myself with high foc or speed. My arrows tune well and shoot well.



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A perfect example of choosing the right arrow to achieve what you want.

Heavy total weight - check
Perfect flight - check
Accurate - check

FOC - who cares
Speed - who cares

The FMJ works perfectly for what jmez wants
 
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