What is spine matching and why do you need it?
October 23, 2023 by Leigh Hauck
“I am sighted in with field points, but when I try shooting broadheads they are all over the place!”
“I can’t get fixed blade broadheads to fly with my field points no matter what I do!”
“Fixed blades just don’t fly well for me, I guess I have to stick with mechanicals.”
Have you ever found yourself saying any of these things?
These are some of the most common issues I hear about from archers, and beginner home-techs who are trying to get their gear dialed on their own. While there are many things that can cause the above issues, 95% of the time the issue comes down to spine matching. What is spine matching? I am glad you asked.
When I tell people that these issues are most likely due to having improperly spined arrows, the response I am always given is “no, my spine is correct, I checked a spine chart before I bought my arrows”. That is great in the sense that you know your spine is close, but you’ve only done about 20% of the work!
Looking at a spine chart should be a starting point in assessing your next arrow build, but it is far from the whole process. There is simply no way that this can be accurate enough. Cutting even ¼" off of your arrow will make the spine stiffer, adding an extra 10 grains to the front of your arrow will make the spine weaker. Bows with large cams have different draw curves and output energy at different rates than bows with small cams.
The point here, is that there is a myriad of factors which go into building a perfect arrow for your bow. This process uses an online software called Archer’s Advantage and will result in building an arrow that is mathematically perfect for your bow.
If you aren’t spine matching, your accuracy is suffering. Period.
Spine matching can literally make you a better archer overnight. If you think a 6” or 8” group is just as good as you can shoot with your bow, spine matching will tighten your groups.
Arrows that are mathematically built for your bow will shoot tighter groups, at longer ranges, and perform significantly better with fixed blade broadheads. Do you want to be able to put fixed blades on your arrows when hunting season comes around and not have to make any adjustments to make them group with your field points? Yes, it is possible... and it’s because of spine matching.
What is arrow spine? What arrow spine do I need?
Arrow spine measures the stiffness of an arrow. A bow that outputs a high energy will need a stiffer spine, which is indicated by a lower spine number. As your draw length increases, you will require a stiffer spine. As your draw weight increases, you will require a stiffer spine. The reason for this is that to attain optimal arrow flight and performance, your spine – or as I like to think of it, the arrow’s ability to absorb and use energy – must match the energy output of your bow. The static arrow spine that you need (the spine number that is printed on the shaft) is only a starting point, and can be found using the spine chart method.
However, just shooting a 300-spine arrow for example is not a recipe for a complete arrow build. Cutting length off your arrow will stiffen the arrow, and adding weight to the front of the arrow will weaken it. Using a spine chart to find the arrow spine that you need is how you need to start the process, but there are so many factors that a spine chart will not account for, that will be crucial in building an arrow that is perfectly matched to your bow.
Spine charts were never meant to be the only step. Stopping at this step, would be like buying a new TV without measuring your wall space. You know you need one bigger than 24” and smaller than 70” so you just get one in that range. Although you will have a working TV, you are very unlikely to have a TV that fits the space perfectly.
How do I spine match?
Spine matching is a bit of lengthy process, but once you figure out each step it isn’t that complicated or difficult. You just need to take your time, apply some logic, and have fun with it!
Spine matching starts using an online software. The one that I use is called Archer’s Advantage, it is a $9 or $10 yearly subscription – a bargain considering the power of this tool.
Archer’s Advantage allows you to input every detail of your current setup, starting with you bow model, draw length, weight, current arrow speed, and then every detail of your current arrow setup right down to the number of vanes and the length of your arrow wrap. I know, this sounds like overkill but trust me when I say it matters. If we are going to put the effort into making our next arrows perfect, you might as well check every box.
From there, Archer’s Advantage will tell you how well your current arrow is spine matched to your bow, and will help you build your new arrows to be mathematically perfect for your bow. The system features every arrow make and model that exists, every bow, every brand and model of vane... this list goes on.
You will be able to play around with any combination of arrow, front end weight, shaft length, draw weight and so much more until you are content with an arrow recipe that you have come up with. You will be able to see a graphical representation of how perfect or imperfect that specific build is for your bow. Would you arrows shoot better if you left the shafts ¼" longer? Would your arrows be more accurate if you switched to 125gr heads? Archer’s Advantage will answer these questions for you in under a second.
No, my bow is perfect. These broadheads just don’t shoot well.
This is another one I hear quite often, and I hate to be the bearer of bad news... but you’re probably wrong. Remember, we don’t tune our bows. We setup our bows, and we tune our arrows. Your bow may be perfectly setup, but if your arrows aren’t tuned (spine matched), then your perfect bow setup means nothing. It would be like giving an MLB player a children’s baseball bat in a game. The player may be the best hitter in the world, and the bat may be top of the line. But if the bat doesn’t fit the player, you can’t expect him to hit a home run with it.
Now, there is the possibility that you are totally right and that the broadheads you are trying to shoot just suck. It isn’t common, but there are broadheads which are made very cheaply overseas, that have very poor quality control and just might never shoot.
Stick with American made broadheads, read the reviews, and look at your own process. If thousands of people are reviewing a broadhead online saying that they are amazing, but they don’t fly out of your bow... the writing is on the wall.
So, what now? Do I have to just buy new arrows?
You might, but you also might be fine. If you realize that your broadhead issues are probably caused by the fact that you haven’t spine matched, then the first step will be to plug your info into Archer’s Advantage and see just how bad it is. There are a lot of things we can do that will impact spine matching without having to do anything to your arrows or buy new ones. Remember, we are trying to match the bows energy output with the energy that the arrow is designed to take.
Years back I created an arrow build that I was very happy with but required me to shoot 55lbs. They were some old shafts I had in my shop that I wanted to put to use, so I was bound by the spine printed on the shaft. I normally shoot in the 70lb range, so this was weird for me. If I shot that arrow at 70lbs, my arrow would have been way underspined. My bow would have been outputting way more energy than the arrow could take, and they would never shoot fixed blades well. I was happy to bring my weight down to 55lbs if it meant I would have perfect flight.
You might not need to buy new arrows right away. You can likely get away with adjusting your draw weight, or changing your point weight. These small changes make a HUGE difference in spine matching, as you will quickly see when you start plugging numbers in Archer’s Advantage. You will still be able to get through this season with your arrows and then spend the winter creating an arrow which is mathematically perfect for your bow.
How do you spine match
If you bring your bow to my shop in Calgary and tell me that you want your field points and fixed blades flying together out to 80 or 100 yards, I will say “no problem, come back in a week” Here is what I will do in that week.
First, I will take measurements of your specs. I will measure the draw weight and length, and then write down every spec of your arrow. Weight, length, point weight, number of vanes, and static spine value (that is the number printed on the shaft).
Second, I will setup your bow. I will make sure it is in time, that the arrow rest is in center shot, that the limb bolts are even, and level your arrow rest. This is what most people would call tuning a bow.
Next, I will do exactly what I describe in this blog. I will plug in your arrow and bow specs into Archer’s Advantage (including current arrow speed, that is a crucial point for the systems calibration). Depending on how close the spine match is, I may adjust your point weight or draw weight to achieve a spine match or I may tell you that you need new arrows if it is really far off.
Once we get your bow set up, and arrows that are spine matched, we go to paper tuning. If you shoot a spine matched arrow, and your arrow rest is both level and in center shot, it shouldn’t take more than a few shots to get a bullet hole. About 60% of the time, I get perfect bullets on the first shot using this method and then I will take a couple more shots to verify.
Once you’ve paper tuned, you are set! Your broadheads will fly like field points (as long as they aren’t some cheaply made overseas rubbish). It works every time, and it is always incredibly fun and satisfying to see it all come together!
If you have any questions or would like to discuss the topic further, please feel free to reach out to us at email@example.com
We are always more than happy to talk arrows and broadheads with fellow bowhunters!
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