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Arrow weight/spine confusion

slonstdy

slonstdy

Well-Known Member
SH Member
Joined
Oct 10, 2018
Messages
1,377
I recently read a post here on hunting arrow weight and most agree around 500 grs is the sweet spot. I never wanted to go down this rabbit hole of bow/arrow tuning but here I am.
So here is my confusion:
My current arrows weigh between 416 - 432 grs, are 10.3% F.O.C. and are the recommended spine for my bow poundage but don't shoot as well as my old xx75 2216's which are 550 - 570 grs and the wrong "weight" (under spined) according to the arrow chart. What I mean by "...don't shoot as well..." is that I notice the tail end sometimes "porpoises" and the arrow doesn't hit the target dead on, it's like it got there from being shot from a different location. The "wrong sized" xx75's fly laser beam straight, albeit slower and really give the target a thump when they hit.
I know the spine is the amt of flex/stiffness in the shaft but shouldn't the physical weight of the arrow be the deciding factor on what is "safe" to shoot in regards to bow damage? The only reason I shoot the xx75's is for volume target practice from up in the tree so I don't have to climb up and down to retrieve arrows. Seems to me that having at least the minimum physical weight to protect the bow would be more important than having an under spined arrow that has a poor flight path. I'm not saying arrow flight isn't important because that's the main reason I'm here trying to figure this out. Are these two separate issues I'm mixing up? :confounded:
I am going to buy new arrows and have them setup at 500 grs or more and see if that helps my arrow flight dilemma.
Can any of you tuning wizards make this simple to understand?
 
I'll be the first to tell you that you're not alone. You have a better chance of winning an arrow spine argument with the wall than a hunter.
Let start with arrow spine. The spine refers to you 300, 350, 400 etc This is the stiffness of the arrow. Ideally the more energy (higher draw weight) you expend into the arrow, the stiffer you want the arrow. Use the arrow chart and keep in mind the broad head weight you are shooting. Higher arrow weight will require a stiffer arrow.
Arrow weight however deals with arrow mass and converted kenetic energy. Arrow weight is calculated by adding up arrow length (gpi is important) broadhead weight, fetching, wraps, nocks, inserts etc.
A total arrow weight in the mid 400's is pretty good. I'm hard pressed to believe you're arrow weight is mid 500's unless your shooting insert weights. FOC closer to 13-15 will help stabilize the arrow a little better. This can be achieved by using a heavier broadhead or insert weight.

Trial and error is really the only way you will figure out what to feed your bow. Bows are like women. They won't ever tell you what they want so you try everything under the sun until they're happy.

Not sure if I answered your question.
Also look up Levi Morgan on YouTube. He is a wealth of knowledge
 
Micro adjust rest up or down till porpoiseing stops. I'm not the most informed person to answer but i have tuned a couple bows. I never really payed arrow spine any attention.....i bought a field point ''test pack'' and just started playing with different weights till i found the weight the bow shot the best/quietest. I have 350spine arrows. My bow likes 630-650 but haven't bought heavier broadheads so I'm at 580 roughly. The 580s shoot good and that's what I'm using this season but the heavier arrows just seen to fly better.... Could just be in my head.

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Yup, just like I thought..rabbit hole! lol
I weighed the arrows on a digital scale to get those weights because I only knew the gpi for the shafts and weight of the broadheads but not the inserts and fletchings so I couldn't mathematically calculate it.
So let me ask this, is there a known minimum value or ratio of arrow weight per bow poundage to safely shoot without harming or stressing the bow?
I'm ok with trial and error testing to find what my bow likes to shoot as long as I know I am within the safe limits of the bows capabilities.
 
62-64 lbs draw weight, easton epics and cabelas carbon hunters (made by easton) 65/80 at 30.5"
 
‘With a compound erring on the stiff side in your arrow selection is not gonna hurt you.With that arrow at that poundage your set up should be pretty simple.125 to 150 gr heads should fly very well.As smoking barrel said around 14 FOC is what i would call a minimum.10 % is getting too close to being a balanced arrow and with a steering wheel on both ends your arrows will be very finicky.
 
Buckhole75 said:
‘With a compound erring on the stiff side in your arrow selection is not gonna hurt you.With that arrow at that poundage your set up should be pretty simple.125 to 150 gr heads should fly very well.As smoking barrel said around 14 FOC is what i would call a minimum.10 % is getting too close to being a balanced arrow and with a steering wheel on both ends your arrows will be very finicky.
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I agree. I would start by adding some point weight to get to mid teens FOC and see if they fly better. This also assuming the arrows/bow have been paper tuned.
 
I like simple. I've been using 100gr heads but I'll put on 125gr field pts and do some testing tomorrow and see if I get better arrow flight
 
Haha not in trouble it just helps makes sure you are fixing the correct problem. Adding point weight is a moot point if you are tearing left or right. Dad never paper tuned and he killed deer consistently every year.
 
I have to admit I"m one of those guys who shoots mechanicals and is lax about bow tuning. Lots of shooting with field pts and a few shots with mechanical broadheads to confirm same POI and that's it, up a tree I go. Years ago tried swapping to the mini fixed muzzy 4 blade and after almost missing my block target at 20 yds I swore mechanicals were it.
 
Smokingbarrel270 said:
Haha not in trouble it just helps makes sure you are fixing the correct problem. Adding point weight is a moot point if you are tearing left or right. Dad never paper tuned and he killed deer consistently every year.
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That's me! So now should I paper tune first?
This rabbit hole just keeps getting deeper...
 
slonstdy said:
I have to admit I"m one of those guys who shoots mechanicals and is lax about bow tuning. Lots of shooting with field pts and a few shots with mechanical broadheads to confirm same POI and that's it, up a tree I go. Years ago tried swapping to the mini fixed muzzy 4 blade and after almost missing my block target at 20 yds I swore mechanicals were it.
Click to expand...
I used to be that way too. I used to torque the hell out of my bow and learned to shoot with a left hold to compensate for torque. Did that for years before I fixed the problem. I still shoot mechanicals most of the time, nothing wrong with that.
 
Alright, first thing tomorrow is throw some arrows thru paper and see what it looks like.
I believe my form is ok because it's only with the "lighter" arrows that I notice movement. My buddy and I had a conversation a year or so ago and I told him I thought it was the 2" vanes I switched to, that they were unable to stabilize the arrow. I never noticed erratic arrow flight when I using arrows with 4" vanes.
 
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