Spine determination

[rjschill]

I recently got a new Elite Kure and it's currently set at 70# and 29" draw. I have a dozen .300 spine arrows that I'd like to use, but I think they are going to be too weak and I'm getting differing results from OT2 and TAP. OT2 is saying if I cut my arrows to 27/28 inches that will stiffen the spine enough to shoot .300, but TAP is saying that the ideal spine is like .228. I think for OT2 I may be missing something with bow performance, but TAP looks pretty straight forward.

Carbon to Carbon = 29 ( could cut to 27.5 or 28)
Point = 125
Insert = 100
Wrap = 5
Nock = 23
Fletching = 23.2 or 28.5

Would .300 spine work if I cut my arrows to 28 inches? If the consensus is .250 will work better and be easier to tune, I'll just go that route.

Thanks!

 

[OR Archer]

Drop your insert weight 50 grains and they’ll be fine

 

[brentr9]

I think you’ll be surprised what the .300 will do. My rampages are 28.25”. I shoot a 343 IBO bow at 29.5” and 70 pounds. I can run up to 275gr total weight up front before I have spine breakdown. 228gr up front tuned the best for me. I shoot 4 fletch (30gr) with a lighted nock (20gr) and wrap (4.4gr).
The online calculators said I would be under spined but my real world testing proved otherwise.
My recommendation would be to test them for yourself knowing what you WANT to shoot and then adjust from there. Your bow will tell you what it wants as long as your bow is properly tuned.

 

[rjschill]

Thanks for the replies. Unfortunately I've already glued the inserts in... I got a little ahead of myself getting excited to get out and shoot.

At what point will the weak spine show itself? I started paper tuning last night and realize I have some problems with my form I need to work out. I'm getting a tail right tear unless I really focus on pulling through the shot. If I can consistently get bullet holes and then move to bareshaft with a tuned bow and good form will the arrows not group well if underspined? Or will I have to fletch and shoot at longer distances?

 

[brentr9]

If your form isn’t correct, you’ll chase circles paper tuning and bare shaft tuning. Make sure you really focus on form during that process.
In my experience, If your bow is tuned and you are paper tuned and bare shaft tuned, your arrow probably isn’t under spined if you are having inconsistent groups. Make sure you spin check your arrows to assess for inconsistencies in the build.
Theoretically you can shoot bare shafts as long as you want to. But once I get outside shooting broadheads, I shoot fletched arrows and go from there.
Also, you can knock your inserts out with a drill bit. Take your nock off, drop an appropriately sized drill bit inside the shaft and whip the arrow shaft so that the bit slams into the back of the insert. Just be sure you’re not around windows (don’t ask me how I know).

 

[rclouse79]

I am now a huge fan of a stiffer arrow. For a couple seasons I thought my bow was untunable. I switched to a 260 spine easton axis 5mm with a 75 grain insert and now a bare shaft groups with my regular arrows.

 

[madkaw284]

Online calculators are just a rough estimate. It sounds like you could be a little in the weak side though.
Like mentioned before, you have to fix you in order to paper or bareshaft tune or you’ll just chase your tail.
You could try using a 100gr point and cutting down to 28” (cut from the rear) and see if that helps


Sent from my iPhone using Tapatalk

 

[dkime]

Switch your spine preference on the top right to "hunting" and they will show even more weak. If you're running a standard insert, cut your arrows to 27" and you will be fine. Or find a heavier vane*

 

[Brendan]

Get out and test before you do anything. Doesn't cost anything.

Shoot field points as compared to fixed blades, and see if you can tune the bow to get them to shoot together reliably and consistently out to longer ranges. I like bareshaft tuning too. You also want to pay attention to group size.

And, if you've got questions about whether you're having an issue, temporarily drop your draw weight down by 5# by turning out the limb bolts (check your manual) and re-do the testing. If tuning issues clean up, and group sizes shrink, you're identifying a spine issue.

If you're weak, then you can shorten the arrow to as short as you can get it without getting broadhead / collar clearance issues, and do the testing again to see if it helps.

Edit: is your nock really 24 grains? The ones on my 300 rampages are 8.5 - lighted nocks maybe?

 

[rjschill]

Get out and test before you do anything. Doesn't cost anything.

Shoot field points as compared to fixed blades, and see if you can tune the bow to get them to shoot together reliably and consistently out to longer ranges. I like bareshaft tuning too. You also want to pay attention to group size.

And, if you've got questions about whether you're having an issue, temporarily drop your draw weight down by 5# by turning out the limb bolts (check your manual) and re-do the testing. If tuning issues clean up, and group sizes shrink, you're identifying a spine issue.

If you're weak, then you can shorten the arrow to as short as you can get it without getting broadhead / collar clearance issues, and do the testing again to see if it helps.

Edit: is your nock really 24 grains? The ones on my 300 rampages are 8.5 - lighted nocks maybe?

Thanks again for the advice/replies. I'm still shooting through paper at short ranges trying to get a bullet hole each time. I found my form issue and am trying to fix that first.

Yes, I'm shooting lighted nocks. Firenocks to be exact.

I feel like I'm in a hurry to get the correct setup, but in reality I need continue to make sure my form is correct through paper, then move to bareshaft and longer ranges and then broadhead vs. field points. If I know my bow is shooting good at that point I can evaluate spine and/or getting new arrows.

 

[gretch6364]

I deleted this post from another thread that I thought was done, but then felt like I was stealing the thread. This one looks older and more on point.

So....250 or 300 Rampage?

65lbs Elite Kure maxed. 80% letoff setting, 29" draw

250 arrow build would be as follows:

29.5" of carbon
10g knock, 4 AAE vanes at 5.7g each
100g point/IW solid
25g IW SS Collar
50g IW HIT

Total weight - 527G

300 arrow build would be as follows:

29.5" of carbon
10g knock, 4 AAE vanes at 5.7g each
100g point/IW solid
25g IW SS Collar
100g IW HIT

Total weight - 518g

Last season I shot a 250 Rampage with the BE FOCUS system and 100g point, 530g total. I was shooting at 28.5" draw and 70lbs from a 2011 Pulse (6" brace), but only 27.5" of carbon. Tuned and shot good. However, the FOCUS system puts all the weight out front and the a 100g HIT is long and all inside the arrow. Will it stiffen it up?

I put all the details in AA and it says 250 is too stiff, but this is the first time I have used the software. Closes archery shop is 3hrs from me, so I am on my own.

Thanks!

Sorry, one other comment. I think the 300 works better from a FOC and total weight standpoint, but I don't want to force a weak spine. My goal is also to keep my speed above 260fps.

 

[Brendan]

@gretch6364 - I think you're fine with a 300. I'm a 29" draw, 72#, and run 300 spine with 175 gr total weight up front. Only difference for me is I run a 27.5" arrow carbon to carbon. My guess is you have room to shorten up the arrow if you want.

 

[gretch6364]

@gretch6364 - I think you're fine with a 300. I'm a 29" draw, 72#, and run 300 spine with 175 gr total weight up front. Only difference for me is I run a 27.5" arrow carbon to carbon. My guess is you have room to shorten up the arrow if you want.

Thanks Brendan. I ordered up stuff to build 6 arrows and will give it a try. Like I said, 300 gives me better FOC (18.9%) while getting to my target arrow weight of just under 520g.

As mentioned, I used the Black Eagle FOCUS system last season with 27.5" of carbon. That gives me total arrow length (not counting nock and point) of 28.75". This is approximately 1/4" short of the end of my riser.

In theory, if I want to be right at the end of my riser for the back of my broadhead, I could go to 29" of carbon. I figured better to be safe, plus the Iron Will collars are 1" long, so I need at an extra inch for that past my rest.

I have not measured my actual draw length on either of my bows. The 2011 Pulse has the 28.5" mods and I am definitely at least half inch longer on the setup of my Kure (I think the Pulse was slightly short).

I may in fact be at 29.5." I switched from a index trigger release to a Stan SX3 as well...which also makes my draw a little longer...probably only 1/4" though.

 

[Brendan]

In theory, if I want to be right at the end of my riser for the back of my broadhead, I could go to 29" of carbon. I figured better to be safe, plus the Iron Will collars are 1" long, so I need at an extra inch for that past my rest.

I have not measured my actual draw length on either of my bows. The 2011 Pulse has the 28.5" mods and I am definitely at least half inch longer on the setup of my Kure (I think the Pulse was slightly short).

I may in fact be at 29.5." I switched from a index trigger release to a Stan SX3 as well...which also makes my draw a little longer...probably only 1/4" though.

I've never paid attention to that end of my riser thing. Remember - I'm your draw length or maybe even longer. Depending on the bow I'm 29-29.25" draw, and the longest arrow I've run in the last 4-5 years was 27.5" carbon to carbon. That is based on torque tuning / testing where my rest ends up and allows me to do it though.

Also - think about how draw length is measured. Take a measurement from the throat of your grip to the inside of your string at full draw. That measurement is 1.75" shorter than DL, If your draw length is 29", you're looking at 27.25". So, take a 27.5" carbon to carbon arrow, add nock, and end of the carbon is .5" ahead of the throat of your grip with broadhead over the shelf.

Also - Not a fan of any outsert personally. I run Brass HIT with the IW Collar. Black Eagle Rampage and Easton Axis.

And - your release doesn't affect your draw length, just your anchor. Unless you're changing the string position relative to the tip of your nose at full draw, which I don't like to do.

 

[gretch6364]

I've never paid attention to that end of my riser thing. Remember - I'm your draw length or maybe even longer. Depending on the bow I'm 29-29.25" draw, and the longest arrow I've run in the last 4-5 years was 27.5" carbon to carbon. That is based on torque tuning / testing where my rest ends up and allows me to do it though.

Also - think about how draw length is measured. Take a measurement from the throat of your grip to the inside of your string at full draw. That measurement is 1.75" shorter than DL, If your draw length is 29", you're looking at 27.25". So, take a 27.5" carbon to carbon arrow, add nock, and end of the carbon is .5" ahead of the throat of your grip with broadhead over the shelf.

Also - Not a fan of any outsert personally. I run Brass HIT with the IW Collar. Black Eagle Rampage and Easton Axis.

And - your release doesn't affect your draw length, just your anchor. Unless you're changing the string position relative to the tip of your nose at full draw, which I don't like to do.

Brendan,

Good info, thank you. A couple things for me personally:

I shoot a fixed blade broadhead (IW S100) and I ordered my arrows pre-cut from Lancaster as I don't yet have a arrow saw. Buddy down the street has a nice setup, so we will trim down if the broadhead fits within the riser with sufficient margins for my comfort level. The IW S100 isn't a particularly wide broadhead, so it will probably fit, but starting out conservative. This is a hunting bow that I shoot field points a ton with, but only for practice for hunting. I understand the benefits of a shorter arrow, but if my BH hits the side of my riser, it won't really matter how well I execute the shot.

I did an actual measurement with my old arrow in my bow, and I need the full length to get the blade to the front of the riser. As mentioned, I have not measured my actual draw length on a draw board, so it may be at 29.5".

This arrow build is not with an outsert, and the FOCUS system is kind of a hybrid system. It does add a good bit of length though because the the entire FP/BH threading is out past the shaft of the arrow. The SS version works great, but I broke a couple of the AL versions, which is the only material available for the Rampage. This is why I am switching to the Iron Will HIT insert and the SS IW Collar. My total arrow length of me old arrows, counting the FOCUS system was 28.75." With this length, my entire fieldpoint (X Spot Easy Pull) is behind the front of my riser.

A couple comments on draw length. My old bow was 34.75" ATA and my Kure is just shy of 32". Due to the change in string angle, to keep my head in a correct position and still touch my nose, my anchor point is further back, which extends my draw length. You are right, it is not due purely to release, but I do find when I draw my old bow, that it was a tiny bit short. It was even shorter before and I was ducking my head, so I put in different mods. I could of gone to a third set of mods, but left it as it was. With the easy adjustments of the Kure in 1/4" increments, I was able to perfect it by trying a bunch of different lengths (closest bow shop is 3 hours from me). I will say that draw length can change with release though, and if you are not switching back and forth, it is fine to not have the releases be coordinated. If your index release sites further forward in your hand the a thumb release (do to neck of release, strap fit, etc.) it will be shorter.

Thanks for all the help. We will see how accurate Archer's Advantage is.

 

[Brendan]

@gretch6364

I shoot Iron Wills and other fixed blades over the shelf. Broadhead fit should not be an issue with the riser unless you're doing something crazy like DeCap Turkey Heads or your bow is way out of tune and you're running your rest too close to the riser.

I know what the FOCOS system is - I am not a fan of any outsert or in/outsert combo and I've tried a bunch. I'm of the opinion they're an inferior design to HIT on their own, or HIT with an Iron Will Collar.

Anchor Point and release should not affect draw length. Think about it, draw the string to the tip of your nose, the start changing release, d loop, etc - the string stays in the same place. You can make a decision to change your draw length to incorporate a different anchor, I don't do that because it compromises reference points that help shoot accurately. Most people get confused by this - but start by understanding what DL is. It's distance from the grip to the string plus 1.75". Has nothing to do with the D loop or release.

 

[gretch6364]

LOL...I have been shooting for 28 years. I understand how it all works.

Thanks again for you help.