Bow Hunting · Guide
Arrow Spine for Beginners
The number printed on the shaft is not a size and it is not a weight. It is the one spec that decides whether your arrows group at all.
Buy a dozen arrows and you will see a number on the shaft: 340, 400, 500, sometimes 600. It is not a length, it is not a weight, and it is not a quality grade. It is spine — a measure of how much the shaft bends — and it is the single spec that decides whether your arrows land in a group or scatter. Get it wrong and no amount of sight adjustment will fix the result. Get it right and a $60 dozen shoots as well as a $200 dozen at hunting distance.
What spine actually measures
Static spine is measured with a standardized test: the shaft is supported at two points 28 inches apart, a 1.94 pound weight is hung from the center, and the deflection is measured in thousandths of an inch. A shaft that sags 0.400 inches under that weight is a 400 spine arrow. One that sags 0.500 inches is a 500.
This means the numbering runs backwards from how most people expect. A lower number is a stiffer arrow. A 340 is stiffer than a 400, which is stiffer than a 500. Heavier draw weights need stiffer — lower-numbered — arrows.
| Spine number | Stiffness | Roughly suits |
|---|---|---|
| 600 | Least stiff | Light draw weights, youth setups, some recurves |
| 500 | Light | Around 40-50 lb at a typical 28 in draw |
| 400 | Medium — the common one | Around 55-70 lb at a typical 28 in draw |
| 340 | Stiff | Heavy draw weights, long draw lengths, heavy points |
| 300 | Stiffest common | 70 lb-plus with long arrows or heavy broadheads |
Why the wrong spine will not group
An arrow does not leave a bow straight. The string pushes the back of the shaft while the front has not started moving yet, so the arrow flexes sideways, then flexes back, oscillating for the first several yards of flight. This is called archer’s paradox, and it is normal — a properly spined arrow flexes just enough to clear the riser and then settles.
Too weak (spine number too high) and the arrow flexes too far, slaps the rest or the riser on the way past, and comes out pointing somewhere unpredictable. Too stiff (spine number too low) and it barely flexes at all, so it does not clear the riser cleanly and steers off in the other direction. Both failures look identical from behind the bow: your arrows do not group, and the pattern changes shot to shot in a way that makes you think your form is falling apart. It usually is not.
Field points hide the problem, broadheads expose it
Picking your spine in three steps
Every arrow manufacturer publishes a spine chart, and they are not interchangeable — a Victory 400 and an Easton 400 are close, but the charts differ because shaft diameter and wall thickness differ. Use the chart for the arrow you are buying. To read it you need three numbers, in this order of importance:
1. Your actual draw weight. Not what the bow is capable of — what it is set at right now. If your bow is a 70-pound bow backed off to 55, you need a 55-pound arrow. Working out your draw weight comes before everything else here.
2. Your arrow length, not your draw length. These are different numbers. Arrow length is measured from the throat of the nock to the end of the shaft, and it is typically your draw length plus an inch or two of safety margin so the broadhead never comes back behind the rest. Longer arrows behave weaker, so adding an inch can push you into the next spine group.
3. Your point weight. Covered below, because it is the one beginners miss.
The part nobody tells beginners: point weight
The weight of the thing on the front of the arrow changes its effective spine. More weight up front means more inertia resisting the string’s push, which makes the shaft flex further — the arrow behaves weaker than its printed number. Most spine charts assume 100 grains, which is why 100-grain broadheads and 100-grain field points are the default everywhere.
The practical rule: if you stay at 100 grains, the chart works as printed. If you jump to 125 or 150 grains, expect to move one spine group stiffer. This is also the reason to practice with field points that weigh exactly what your broadheads weigh. A 100-grain field point and a 100-grain broadhead fly close enough to sight in with; a 100-grain field point and a 125-grain broadhead do not, and you will discover the difference at the worst possible moment.
| Change you make | Effect on how the arrow behaves | What to do |
|---|---|---|
| Increase draw weight | Arrow acts weaker | Go one spine group stiffer |
| Cut the arrow shorter | Arrow acts stiffer | Usually fine - recheck the chart |
| Add 25-50 grains of point weight | Arrow acts weaker | Go one spine group stiffer |
| Switch to a heavier insert | Arrow acts weaker | Count it as point weight |
| Change nothing but the fletching | No spine change | Nothing |
Getting it checked for free
Here is the shortcut that saves a first-season hunter the most money and grief: take your bow, exactly as it is set, to a local archery shop and ask them to spec your arrows. It takes them ten minutes, they will measure your real draw length on the bow rather than the number you calculated, and they will cut the shafts to length and install the inserts. Many shops do it free with an arrow purchase, and it removes every variable at once.
If you are buying online instead — which is entirely reasonable — a 400 spine at 28 inches with a 100-grain point covers the large majority of beginner compound setups running 55 to 70 pounds. That is the sensible default, and it is why every arrow in the beginner arrow roundup is a 400. Confirm it against your specific chart before you order a dozen, and once you have them, put them through your own target often enough that you would notice if something changed.
Frequently asked questions
What does arrow spine mean?
Spine is how much an arrow shaft bends. It is measured by supporting the shaft 28 inches apart, hanging a 1.94 pound weight from the center, and recording the deflection in thousandths of an inch. A shaft that sags 0.400 inches is a 400 spine. Lower numbers are stiffer arrows.
What arrow spine do I need for a 60 lb bow?
A 400 spine covers most 60 pound compound setups at a typical 28 inch arrow length with a 100 grain point, and that is the sensible default. Confirm it against the chart for the specific shaft you are buying, because charts differ between manufacturers, and adjust one group stiffer if your arrows are long or your points are heavier than 100 grains.
Is a lower arrow spine number stiffer?
Yes. The number is a deflection measurement, so it runs backwards from what most people expect. A 340 shaft bends less than a 400, which bends less than a 500. Heavier draw weights, longer arrows and heavier points all need stiffer - lower-numbered - shafts.
What happens if arrow spine is wrong?
Your arrows will not group consistently, and the pattern will change shot to shot in a way that looks like bad form. Too weak and the shaft flexes into the rest or riser on the way past; too stiff and it does not clear cleanly. Field points often mask the problem, and fixed broadheads expose it immediately.
Does point weight change arrow spine?
It changes effective spine, not the shaft itself. More weight on the front means the shaft flexes further under the string's push, so the arrow behaves weaker than its printed number. Most charts assume 100 grains - moving to 125 or 150 grains usually means going one spine group stiffer.
Sources
Keep reading
Not sure where to start?
The beginner gear checklist walks you through exactly what a first-season hunter needs — essentials first, nice-to-haves later, with one safe-default pick per category.