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Discussion Starter · #1 ·
I have my bow tuned to 300 spine arrows, bareshafts hitting with fletched, fixed broadheads flying really well.

I have some 350 spine shafts I was shooting in my last bow and bareshafts will hit dead straight in the target on a vertical line with fletched, but really Nock low.

Both 300 and 350 spine are same length (27.5") and same 22 grain inserts. Both are Victory VForce. 125 grain points.

SR6 at 62 pounds and 29" draw, Vaportrail Pro V.
The Victory spine calculator says I should be using a 350 spine unless I go up to a 200 grain point.

Why would the 350 spine have such a bad Nock low compared to the 300?
 

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I have my bow tuned to 300 spine arrows, bareshafts hitting with fletched, fixed broadheads flying really well.

I have some 350 spine shafts I was shooting in my last bow and bareshafts will hit dead straight in the target on a vertical line with fletched, but really Nock low.

Both 300 and 350 spine are same length (27.5") and same 22 grain inserts. Both are Victory VForce. 125 grain points.

SR6 at 62 pounds and 29" draw, Vaportrail Pro V.
The Victory spine calculator says I should be using a 350 spine unless I go up to a 200 grain point.

Why would the 350 spine have such a bad Nock low compared to the 300?
outside diameter.
VForce 300 spine outside diameter = 0.304 inches.
VForce 350 spine outside diameter = 0.298 inches.

Different outside diameter.
BUT, u say, its ONLY 0.006 inches smaller OD. 6 thousandths of an inch, can't POSSIBLY make any difference, right?

Ur arrows are telling you different.
Retune for the 350 spine arrows, if you plan to use the 350 spine arrows.

U are tuned for the 300 spine arrows.

1) drop draw weight for the 350 spine arrows...until you find the draw weight that works best.
2) drop the field point and broadhead weight...until you find the weight that works best.
3) play with arrow rest height...until you find the weight that works best for 350 spine.
4) adjust cam TIMING...until you find the cam TIMING that works best for 350 spine.
 

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I have my bow tuned to 300 spine arrows, bareshafts hitting with fletched, fixed broadheads flying really well.

I have some 350 spine shafts I was shooting in my last bow and bareshafts will hit dead straight in the target on a vertical line with fletched, but really Nock low.

Both 300 and 350 spine are same length (27.5") and same 22 grain inserts. Both are Victory VForce. 125 grain points.

SR6 at 62 pounds and 29" draw, Vaportrail Pro V.
The Victory spine calculator says I should be using a 350 spine unless I go up to a 200 grain point.

Why would the 350 spine have such a bad Nock low compared to the 300?
often, a lighter spine has a thinner wall diameter but same outer diameter (to accommodate universal sized inserts and nocks), therefore the outer diameter of more limber shafts is typically less

if you put them on the bow, then they will be slightly angled downward on the rest compared to the larger outer diameter and stiffer spine, this will cause bare shafts to hit low because you've increased the downward angle of the arrow
 

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You know, I never expect a different arrow to shoot perfectly out of my bow especially when there is a major spine difference or diameter difference between the arrows. Have I been surprised, Hell Yes!!! I have had a few setups that shot perfectly with two totally different arrows where the bow was tuned to one of them.

I wouldn't read to much into the 350 spine arrow shooting different, It is different in spine and possibly other issues such as the diameter of the shaft like the other guys mentioned.
 

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I was messing around the other day with some different arrows. My bow is tuned with a easton hexx which is a 6mm arrow. Well I had built some victory rip tko and some vap tko. The rip is a .204 and the vap is a .166. I built them to all be about the same weight, but they all have a different point due to the od. Here's a picture from 40 yards. I just thought it was interesting.


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Discussion Starter · #6 ·
often, a lighter spine has a thinner wall diameter but same outer diameter (to accommodate universal sized inserts and nocks), therefore the outer diameter of more limber shafts is typically less

if you put them on the bow, then they will be slightly angled downward on the rest compared to the larger outer diameter and stiffer spine, this will cause bare shafts to hit low because you've increased the downward angle of the arrow
In my case it's the opposite of that. The smaller OD 350 spine is hitting higher (Nock low) which is why it doesn't make sense to me.
 
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In my case it's the opposite of that. The smaller OD 350 spine is hitting higher (Nock low) which is why it doesn't make sense to me.
Check arrow weight. I have a set of 20 arrows I practice with every day. A while back I always had one group set that impacted high (they are arranged in a 4 groups of 5). Couldn't figure out why till I realized one day that group of arrows was a different model that was lighter. I ran them through the chrono and of course they were faster...I replaced them with the same model arrows as the other 3 groups and no more high point of impact with that group.
 

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Discussion Starter · #9 ·
Check arrow weight. I have a set of 20 arrows I practice with every day. A while back I always had one group set that impacted high (they are arranged in a 4 groups of 5). Couldn't figure out why till I realized one day that group of arrows was a different model that was lighter. I ran them through the chrono and of course they were faster...I replaced them with the same model arrows as the other 3 groups and no more high point of impact with that group.
It isn't about the weight. I know the 350 spine are coming in 25 grains lighter than the 300 spine, so I'm not expecting them to group together.

I can shoot a 300 spine bareshaft and it hits with a 300 spine fletched arrow.

When I shoot a 350 spine bareshaft it hits higher than a 350 spine fletched arrow and has a pretty severe Nock low angle.
 

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outside diameter.
VForce 300 spine outside diameter = 0.304 inches.
VForce 350 spine outside diameter = 0.298 inches.

Different outside diameter.
BUT, u say, its ONLY 0.006 inches smaller OD. 6 thousandths of an inch, can't POSSIBLY make any difference, right?

Ur arrows are telling you different.
Retune for the 350 spine arrows, if you plan to use the 350 spine arrows.

U are tuned for the 300 spine arrows.

1) drop draw weight for the 350 spine arrows...until you find the draw weight that works best.
2) drop the field point and broadhead weight...until you find the weight that works best.
3) play with arrow rest height...until you find the weight that works best for 350 spine.
4) adjust cam TIMING...until you find the cam TIMING that works best for 350 spine.
Exactly this ^^^.

Some rest designs are more forgiving than others too. Some shooters seem to be able to interchange diameter sizes with few significant differences in POI or flight dynamics.

My rest is not forgiving at all. I can't even shoot 300 VAPs and 300 VAP TKOs in the same bow, with same grain TAWs, because the shaft outside diameters differ by only .005". I had to choose the VAP TKOs for my primary bow, and the standard VAPs for my backup in order for both bows to tune properly. (Same rests on both bows).

So which would I rather have forgiveness or precision? I'll take precision all day long.
 

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Then most of you guys would think it’s impossible to shoot a 2315 and a 2712 aluminum arrow at 18 meters and both hit the x . No more than those two arrows od are , it would be very easy to get them hitting very very close together. But question is , why? I only tune the arrow I’m gonna shoot. If I change arrows, I retune. But if they are close, it doesn’t take much.
 

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It may be the way the arrow oscillates. The lighter spine is in a different node of oscillation when coming off the bow with the nock travel and nock setpoint. A similar thing happens with rifles. When you change the powder charge , it can change the way the barrel oscillates, so when the bullet leaves the barrel it has a slightly different orientation to the bore as it leaves, or the difference in gas pressures surrounding the bullet, different rpm etc. A bareshaft is so sensitive, that is why they are good for helping to get your bow in tune with the arrow, so that the the forces applied to the shaft are as close to linear as possible. Makes the correction forces needed less. You may have a different experience with two different arrows of different spine, just by the way they act dynamically when shot. Static spine, dynamic spine. You got to shoot some to see what happens. Off the drawing board, out of the lab, into the field. Things do not always work out the way we think they should. One possibility anyway.
 

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I have an assortment of shafts I play with in my collection of 9 Hoyts, .400, .350, .340, 300 spine, .204 and .245 ID, Victory, Gold Tip, and Beman/Easton shafts. 50 or 60lb PW bows with 330fps to 350fps ATA ratings. I swap them around year to year trying different tip weight weights. POI can shift up or down, but I'm often surprised by how much any given combination can affect the changes, and the general lack of predictability. I suspect that the differences are related to the dynamic properties, which respond to small variations in the tuning and mechanical properties of a given combination of shaft properties. And sometimes, stiffer/weaker spine, different diameter, tip weight, doesn't make any difference at all. ??

Let's me know, I don't know it all.
 

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It's the diameter and the spine. Different arrows react differently, especially different spines. It will fly completely different based on the flexibility of the shaft. It may hit near the other one but your vanes are working harder to keep it straight. Shoot what your tuned for or tune to what you want to shoot. Good luck!
 

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Discussion Starter · #16 ·
Call me dumb. But your 300’s are all tuned up and shooting good, if I comprehend what you wrote correctly, so.. why not shoot the 300’s and call it a day?


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Just messing around and thinking about going back to a 350 spine.

The reason I say it's a weird bareshaft reaction is that since the 350 spine is smaller OD, it SHOULD come off the bow Nock high when the rest is set for the 300 spine, but it's doing the opposite.
 

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It may be the way the arrow oscillates. The lighter spine is in a different node of oscillation when coming off the bow with the nock travel and nock setpoint.
Aluminum 2315 and Aluminum 2712. MUCH lower natural frequency (rate of oscillation) than a carbon arrow.
Aluminum 2315 and Aluminum 2712. Might greater amplitude during the oscillation, at the lower frequency, compared to a carbon arrow.

Due to the materials of construction (ALUMINUM alloy), the location of the front node (location where the arrow shaft has zero amplitude) will be VERY different than a carbon shaft.


Just messing around and thinking about going back to a 350 spine.

The reason I say it's a weird bareshaft reaction is that since the 350 spine is smaller OD, it SHOULD come off the bow Nock high when the rest is set for the 300 spine, but it's doing the opposite.
The 350 spine is SMALLER OD,
and also a WEAKER spine. So the SMALLER OD arrow bends DIFFERENT to the LARGER OD arrow.

It's called DYNAMIC SPINE. You cannot tune arrows JUST based on assumptions for outside diameter.
Switch to a different arrow, REDO the tuning
and do not exact to do ZERO tuning and expect the same bareshaft reaction. RETUNE for the 350 spine arrow for best results.

THe cam TIMING for the 350 arrow is no good. FIND the new cam timing.
The arrow rest height for the 350 arrow is no good. FIND the new arrow rest height.
The draw weight for the 350 arrow is no good. FIND the new draw weight...for best results with the 350 arrow.
 

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Have you tried flipping arrow over?
Try turning the nock 45 degrees and shooting it again. Then another 45 etc to see if it will change its nock low.

If you have a drop away I would say you are getting a very odd reaction. I bareshaft tune a lot of others bows with my 4 mm bareshafts I have. I try to leave them just a shade nock high. Then when they shoot thier bigger diameter arrows it is perfect.

I have seen old school two prong rests do some weird stuff especially if they are set up stiff.
 
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