Everything You Need to Know About Arrow Spine Selection
- 02 Jan, 2017
Being able to navigate the waters of arrow spine selection can be tricky for beginners. This brief guide should set you on the path to ensuring you buy the correct arrow for your particular bow.
Buying archery gear, especially for the beginner, can be a bit daunting. Depending on what you’re buying, you may need to consider draw weight, arrow speed, point weight, arrow length, bow weight, or other details of your shooting rig. That can be a lot to handle right off the bat. One area of archery that may be especially confounding for a beginner is arrow spine selection. What the heck is arrow spine, what do the numbers mean, and what’s right for your bow? These are all questions every archer should have an answer to, although not always the same answer.
Arrow spine is simply a reference to the amount of bend an arrow has. All arrows need to have some flexibility to allow them to fly straight. With today’s high speed cameras, you can actually watch them flex in slow motion. This bending used to be called the archer’s paradox. These days, compound bows no longer face the archer’s paradox since they have center-shot risers. There is quite a bit of information on the difference between the old archer’s paradox, and how it doesn’t apply to modern compound shooters, if the subject interests you. The main point remains true though, no matter what bow you shoot, all arrows need flexibility. When it comes to selecting the correct arrow spine, the trick is to match the amount of bend an arrow has to your bow.
When manufacturers make arrows, they give certain batches more or less flex to accommodate different bows. You can identify the arrow you’ll need for your bow by looking at the number stamped on the arrow. Numbers such as 350, 400, or 750, indicate the arrow spine. These numbers are determined by the manufacturer after putting the arrow through a static flex test. Basically, in this test the manufacture takes an arrow 29” long and suspends it between two points roughly 28” apart. Next, they suspend a 1.94 pound weight in the center of the shaft to see how much it bends. They record the measurement and it becomes the spine. You can watch an independent test in this video along with other information on arrow spine.
The tricky part of the arrow spine selection process is the fact different companies have different methods of marking their arrows. For example, Easton marks their arrows by how much they bent. This means an arrow with a spine of 750, bent .75 inches during the test. On the other hand, companies like Carbon Express do the opposite. In their system arrows that flexed more actually have lower numbers. So a Carbon Express 750 would have bent not nearly at all. It all depends on what company you are buying arrows from.
So how much flex should your arrow have? That depends on the type of bow you shoot, the poundage you are shooting, the point weight you use, and your arrow length. As a rule though, heavier bows will need a shaft that flexes less than a lighter bow. The best way to select your arrows is to use the spine chart of your arrow’s manufacturer. For example, if you are going to buy a Carbon Express shaft, you will use this chart. Since there are many variables that come into play you first need to do a little math with their system. Start on page 3 and add up your score to determine your “adjusted bow draw weight”. You’ll find it will likely be very close to the actual weight you pull. Once you’ve done that you need to go to the next page of the chart.
Most charts for arrow spine selection are pretty much the same. Compound bow weights are on the left and traditional bow weights are on the right. Find the weight range that you are shooting on the correct side of the chart. Next, match that draw weight with the correct arrow length you shoot. That will give you a few options of arrows with the correct spine for your shooting rig. Personally, my adjusted draw weight for my compound bow is 67 pounds and I shoot a 28 inch arrow. The corresponding box has six different arrows that would match my rig including the PT 6075, CR 350, and the HE 350. With those codes in mind I can go to the final page in the chart and match it to the actual arrow I want. The HE 350 for example would be the Heritage arrow with a .32 spine. As mentioned, each chart will be different for each company.
Arrow spine selection may at first seem a little complicated. There are lots of numbers to take into consideration. The charts can also be a little puzzling as well. Once you understand what you are looking at though, the process is pretty easy. Matching a correctly spined arrow to your bow is paramount in achieving the best accuracy you can. In a sport that’s all about accuracy it’s something you have to get right.