Am i Under-spined?

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Feb 17, 2023
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OK, so not that i'm looking to switch up my set up as bow shoots well, i get good groups out to 80-90y, after that it opens up a bit, but that's also on me being newer to archery. but i am wondering..... am i under-spined?
So for experts on here with more experience, what is your opinion?
Bow: Bowtech Carbon ZION 70lbs model - set at about 65 lbs (i just put on new string, so after another day or two at the range i'll re-check and will adjust to stay at 65lbs as i feel comfortable there)
Arrows; Easton AXIS 5mm 300 spine / 30.5" (knock throat to end)
Arrow Weight: 501gr (all my arrows are with in 1gr, ranging 501.2 up to 502.3)
Bow Draw lengths set at: 30"
Speed: 255 fps (before i changed string, i'll re-chrono soon)
Broadheads: 125gr
Release: Finger/trigger

Hunting broadheads: 3blade fixed and Sevr mechanicals, both fly well and group very tight with field points out to 60y

seems like when i look at the charts or input my information into spine calculators, i'm told 250-300 is the recommended range.
300 spine seems to work just fine for me currently, is it even worth trying AXIS 5mm 260 ?
my main concern is that i don't want to go any heavier with my arrow set up, and going from 300 to 250, it'll jump 0.8gpi adding another 24grains to my total set up (going to 525 set up?)

thoughts?
thanks
 
Last edited:
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Shoot 100grn heads and see if you notice any difference


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Joined
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just out of curiosity, what type of differences should i be looking for?
groups shifting point of impact?? tighter vs open groups? higher impact because of lighter arrow?

Underspine you will usually not group well , Arrow flight will be erratic and the excess flex could effect the amount of penetration you get. Drop down to 100 grn see what it does. Better to be over than under spined if in doubt.


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TuckTruck

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I’m shooting a Mathew’s halon maxed at 70# shooting 400 spine fmj arrows with 125 gr heads. This has been my setup for 8 years. I did the same thing as you a few years ago reading arrow charts. I went to my shop and we did a few tests and determined that everything was fine, the owner said if it ain’t broke, don’t fix it.
 
OP
R
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And it very well could be that my set up is perfectly fine as is and has been working well for me.
But it’s fun to test new gear/set ups/ammo etc.
going to the range tomorrow. I’ll try switching to 100gr fp down from 125gr to see if I can notice any difference
 

Wrench

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Do your groups drift right or left as distance increases? What's the arrow do on paper?
 
OP
R
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No drifting if im shooting well that day.
With new string on shop tech that bullet holes punched so paper tuned.
Again: I didn’t have any issues up to this point. But just wondering if I could be under spines and if it’s worth trying stiffer arrow?
 

5MilesBack

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Your setup either works or it doesn't. Sounds like yours works fine, don't mess with what works.....unless you just want to test stuff out for the heck of it. I do that all the time with all kinds of gear, but rarely find anything that works "better" than what I was already using.
 
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Try dropping point weight or even cut 1” off the front of your arrow to stiffen. Your draw length is 30” but you shoot a 30.5” arrow? If that’s the case then you can shoot a 29” arrow just fine.
 

Bump79

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Your setup either works or it doesn't. Sounds like yours works fine, don't mess with what works.....unless you just want to test stuff out for the heck of it. I do that all the time with all kinds of gear, but rarely find anything that works "better" than what I was already using.
Oh man. This describes everything I do. More arrow weight, less arrow weight, more FOC, different broadheads. I land at the same spot. I put more time and effort into hunting now and am no kill no more stuff...

Biggest lie to people is the "always be tinkering" mindset. Find something that works and do minimal tinkering. It's just designed to push products and reality is we're fighting for that 2-4% better for a hell of a lot of time and money.
 

Zac

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Oh man. This describes everything I do. More arrow weight, less arrow weight, more FOC, different broadheads. I land at the same spot. I put more time and effort into hunting now and am no kill no more stuff...

Biggest lie to people is the "always be tinkering" mindset. Find something that works and do minimal tinkering. It's just designed to push products and reality is we're fighting for that 2-4% better for a hell of a lot of time and money.
Yes, never be tinkering is a far better mantra. OP you sound full of shit, but maybe you really are shooting that great with that tiny little bow.
 

Beendare

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I see posts like this and they always lack legit info- so who knows.

We know the OP is shooting an arrow that hangs a long ways over his rest. Sure that can work but experienced guys don’t do that.

He states that he can shoot pro level at 60y- so why ask the question? Or are those “good groups” in a two foot circle?

Did he BH tune, check cam rollover, etc…we just don’t know. If not, that speaks to experience level.

Are we talking shooting one or 2 BH’s or just a couple shots? Those mech heads are harder to shoot many times in practice without destroying them…so my guess is only a few shots which is not enough to really know whats going on.

Then, if they go through all of the BH tuning steps…they answer their own question.

My apologies to the OP for using him as an example, but these diagnostic posts always lack pertinent info.
 
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MattB

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Biggest lie to people is the "always be tinkering" mindset. Find something that works and do minimal tinkering. It's just designed to push products and reality is we're fighting for that 2-4% better for a hell of a lot of time and money.
I largely agree with this. There is value as a newbie in trying different things to optimize and to learn how changes in equipment changes arrow flight etc., but past I point I really do think tinkering becomes detrimental to success.

Some guys are more about the process than the result in this regard.
 
OP
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No drifts. Per shop tech on paper it was a bullet hole so all good.
Anyways I went out today to the range. Lil windy so was hard to tell if it was me or tune not hitting bulls eyes out to 60y. But overall shot pretty good.
One thing I was way off on was the speed I thought I had. I’m shooting 255fps with my set up
Changing from 125 to 100 points only bumped the speed from 255 to 261
 

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OP
R
Joined
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I see posts like this and they always lack legit info- so who knows.

We know the OP is shooting an arrow that hangs a long ways over his rest. Sure that can work but experienced guys don’t do that.

He states that he can shoot pro level at 60y- so why ask the question? Or are those “good groups” in a two foot circle?

Did he BH tune, check cam rollover, etc…we just don’t know. If not, that speaks to experience level.

Are we talking shooting one or 2 BH’s or just a couple shots? Those mech heads are harder to shoot many times in practice without destroying them…so my guess is only a few shots which is not enough to really know whats going on.

Then, if they go through all of the BH tuning steps…they answer their own question.

My apologies to the OP for using him as an example, but these diagnostic posts always lack pertinent info.
All good. Just saw few other notes questioning ability, no issues with that.
I have no doubt that there are tons of pros o here who tune their own bows.
I must fall In The other group of majority of regular guys who rely on shop experts to tune/set up my bow, and then I shoot/adjust enough to get proficient.
Either way. Seems like my spine/weight is spot on, I’m happy with my groups.
👌

To answer specific of shooting BHs vs FPs. No I do t just shoot 2 shots. When I hit the range for broadhead practice I shoot till I can’t shoot anymore due to arms being tired/shaking.
Sevr’s by the way are super easy to practice with, they have a little screw that holds blades in place so you can shoot them all day wout any damage as long as the range has dedicated/allows BH targets
 
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I don’t tinker around with stuff once it’s set where I want it. I went through that bow tinkering phase as a teenager. 🤣 I would still cut that arrow shorter though. Cutting it to 29” will cut off about 15 grains. I know axis 340 are 9.5 grains per inch. Assuming 300’s are at least 10 grains per inch. Having an over spined arrow on a compound is better.
 
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