Building the Perfect Arrow for Your Bow with Spine Matching
How do you build hunting arrows?
The typical process for most people to buy archery arrows for their compound bow as follows. You go to the shop, tell them your draw weight, a bow tech might measure your arrow length, and they send you on your way. This is the ‘easy’ way.
This is the bare minimum when it comes to assessing the right arrow. This simple method starts and ends with a spine chart, which considers your approximate point weight, draw weight, and arrow length to tell you what arrow spine matches your bow.
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 10 grains to the front of your arrow will weaken the spine.
Bows with large cams have different draw curves and output energy at different rates than bows with small cams. The list goes on. The point here is that there is a myriad of factors that go into building a perfect arrow for your bow. This process uses an online software called Archer’s Advantage and will build a mathematically perfect arrow for your bow.
Why should you spend time building your bowhunting arrows.
Now, you may be saying to yourself “my arrows fly fine using the simple method; why would I spend the time and energy doing this?” The answer lies in what I like to call the Last 5 %.
The Last 5% is all the small things that often get ignored in archery. Far too often, archers find themselves getting their gear to a point where it is ‘good enough’ or just accepting that they aren’t good enough to shoot softball-sized groups at 80 yards and move on.
The Last 5% is a compilation of skills and techniques that will make you achieve your archery goals, and spine matching is the first crucial step.
What is spine matching.
Spine matching can make you a better archer overnight.
Spine matching will tighten your groups if you think a 6” or 8” group is just as good as you can shoot with your bow. Arrows that are mathematically built for your bow will shoot tighter groups at longer ranges and perform significantly better with fixed-blade broadheads. So, without further ado, let’s get into the nitty-gritty.
1. What is an arrow spine? What arrow spine do I need?
The Arrow spine measures the stiffness of an arrow.
A bow that outputs high energy will need a stiffer spine, which is indicated by a lower spine number. 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 think of it, the arrow’s ability to absorb and use energy – must match the energy output of your bow.
The arrow spine you need is only a starting point and can be found using the spine chart method. However, shooting a 300-spine arrow is not a recipe for a complete arrow build.
Cutting the 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 you need is how you 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.
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 get one in that range. Although you will have a working TV, you are unlikely to have a TV that fits the space perfectly.
2. Setting Yourself Up with Archer’s Advantage
I want to preface this by saying that we are in no way affiliated with Archer’s Advantage; they don’t even know we are doing this write-up. Archer’s Advantage is a tool that I have used for many years, long before I ever worked with Tooth of the Arrow, and it has become the most valuable tool in my arrow-building toolbox. It is based on a yearly subscription of I believe $9.99, and that is a bargain considering the power of this tool.
The first step is to go to the ‘Setup’ tab on the left column of tabs and click ‘Add Setup’. Name your bow, and then input your arrow's current details. This information you are inputting must be for your current arrow setup, not the one you will be building. Put this information in as accurately as possible.
If you don’t know your insert or outsert weight, go to your arrow manufacturer's website, and you will be able to find the weight of your components that match your arrow.
If you have an arrow wrap or a fourth vane, make sure you add that too. This tool is so powerful that even the 4-6 grains that make up a vane or a wrap will make a difference.
It is also crucial to note that all arrow length measurements are carbon-to-carbon and do not include nocks or inserts.
Once you are confident that all the tabs under ‘Arrow Configuration’ are filled out accurately, move to the ‘Bow Configuration’ tab to the right of the ‘Arrow Configuration’ tab.
Here, you will want to input everything again as accurately as possible. I built a drawing board for about $25 to measure my draw length down to 1/8” at home and bought a cheap bow scale on Amazon to measure my draw weight. Input that information, and then comes the most crucial step.
Archer’s Advantage will estimate your ‘Current Arrow Speed’ on this tab, but you must measure your true arrow speed with the arrow that you just entered and put it into the system.
Any pro shop should have a chronograph that you can use, or if you are building a home shop, it is another great tool. Once you have entered your actual ‘Current Arrow Speed’, Archer’s Advantage will have calibrated all your information, and you will be ready to figure out your next arrow build.
Details from my personal setup
3. Using the Shaft Selector
The next step is to click on the ‘Shaft Selector’ tab on the left. This will automatically show you the spine-matching data of your current setup of the arrow you just entered.
Your arrow will likely show either weak or stiff to some extent. You can see here that my arrow setup is ‘Marginally Weak’. That is because I increased my draw weight in the offseason from 65 lbs to 71.33lbs. You can see that when I make that adjustment, my arrow is suddenly in the ‘Optimum Spine’ range.
This is because a ‘weak’ arrow means that your bow is outputting too much energy for that arrow. Similarly, a stiff arrow means that your bow is not outputting enough energy to make that arrow flex in flight as it is designed to. In other words, every arrow has an exact energy output at which it will fly optimally. It may fly well across a range of draw weights/point weights, but there is only one exact setup that will make it fly mathematically perfectly. This is precisely the definition of spine matching.
From here, you can play around with any arrow setup you could dream up. This is the most fun part of arrow building for me. Pick your brand first and then your arrow model. From there pick the spine that the arrow manufacturer’s spine chart says you should be using.
As mentioned earlier, this is a fine starting point, but nothing more. Using only the spine chart provided by the arrow manufacturer that you are shooting is also crucial, as they are not universal across brands. If you are right in between spines, go with the stiffer one (a lower number is always stiffer, i.e., 250 spine is stiffer than 300)
The point weight is the sum of your field tip/broadhead weight and your arrow insert and will be set to show your old arrow’s point weight. Play around with this but keep the sum of parts in mind. Suppose you are planning on using a 110gr. insert and a 125gr. broadhead, then your point weight that you enter here must be 235gr.
For arrow length, I will put my bow on my draw board and bring it to full draw. I will then measure the length from my nocking point to my arrow rest. This is the absolute minimum length that your arrow can be without falling off your rest, so add ½"-¾" to this length and use that as a starting point for your build.
Remember, adding length will weaken the spine. Cutting length will stiffen it. You can use ¼” increments to make the fine adjustments needed to get your arrow in the ‘Optimum Spine’ range.
Play around with this until you have found an arrow setup that puts you in the ‘Optimum Spine’ to ‘Marginally Stiff’ range. I tend to build my arrows on the right edge of the green ‘Optimum’ area because arrows weaken naturally over time just by shooting them. If you build a slightly stiff arrow, it will be optimum after not many shooting sessions.
Have you ever seen a warning to ‘Flex It First’ on some arrows? This is a big part of the reason that warning exists. For this reason, it is always better to be slightly stiff than to be slightly weak.
4. Tips for Designing the Perfect Arrow for Your Bow
There are certain things I like to keep in mind when going through this process of playing around with the Shaft Selector.
First, I always keep an eye on the ‘Est. Speed’. So long as you have entered your actual arrow speed in the ‘Bow Configuration’ portion, then this will be a very accurate estimate. Arrows fly best in the 270fps to 280fps range.
Just as any projectile has a speed at which is designed to fly optimally, arrows are no different, and this range tends to be where we see the best performance particularly when you are shooting a fixed blade broadhead on the front, which can magnify shortcomings in your bow or arrows setup.
As you have probably heard me mention, the Golden Rule of Arrow Building comes into play here. Since I want my arrow flying 270fps to 280fps, I want to shoot the heaviest arrow I can, keeping my speed inside that range.
I will achieve this mostly by adjusting my point weight. I will look at the options I have available for inserts/outserts as a starting point. I like to shoot stainless steel or brass inserts, as they are tough materials that are unlikely to bend. Aluminum inserts commonly come with your arrows, but they are very light and prone to bending. I recommend looking into aftermarket components from brands.
Choosing stainless steel or brass will naturally put your insert/outsert weight in the 85gr.+ range. This usually is about right for attaining that arrow speed we are looking for anyways.
After this, I will look at my options for broadhead weight which are usually in 25gr. Increments. Play around with your options until you find what the spine meter says is ‘Optimum’ or ‘Marginally Stiff’. You can also adjust your draw weight to achieve perfection. I have no problem dropping my draw weight by a pound or so if it means my spine matching will be perfect.
This is the complete process of spine matching. It is the only way to ensure that your arrow and bow are mathematically perfect for each other. It is also a crucial step to making yourself a better archer.
With spine-matched arrows, you will shoot tighter groups than before. Your broadheads will fly better, and your arrows will paper-tune better than before.
It is a lot of work, but it is such a fun process once you see the results, and it feels great to put that effort into your setup. You will certainly take more pride in your next harvest and know that you took a huge step towards that Last 5% of becoming a more accurate and ethical archer.
If you found this article interesting, we also put together a great video.
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!