Wrong arrow spine is one of the most common — and most misunderstood — problems in bowhunting. An arrow that's too stiff or too weak won't fly consistently, no matter how well you tune your bow or shoot your form. This guide walks through spine selection from the ground up, with a comprehensive chart for every common setup.
What Arrow Spine Actually Means
Spine refers to how much an arrow bends when force is applied. The AMO/ATA standard measures spine by placing a 1.94 lb weight on the center of a 29" arrow supported at both ends and measuring the deflection in inches. Counterintuitively, a lower spine number means a stiffer arrow — a 300 spine bends less than a 500 spine.
When a bow fires, the arrow flexes around the riser in a phenomenon called the "archer's paradox." The right spine allows the arrow to flex appropriately and recover straight on the way to the target. Too much flex (weak spine) and the arrow fishtails. Too little flex (stiff spine) and the arrow kicks off to one side.
The Four Variables That Determine Correct Spine
Draw Weight
More draw weight = more energy transferred to the arrow = more flex = need for a stiffer spine. The primary driver.
Draw Length
Longer draw length increases the lever arm and arrow flex. Add 5 lb of effective draw weight for each inch over 28".
Point Weight
Heavier points (broadheads, heavy field tips) increase flex at the front of the arrow. Go one spine stiffer for points over 100 gr.
Arrow Length
Longer arrows are weaker (more flex). Shorter arrows are stiffer. Cut length affects spine rating significantly.
Arrow Spine Chart: Draw Weight × Draw Length
The table below assumes a 28" arrow cut to length with a 100 grain point. Adjust as noted in the rules below.
| Draw Weight | 24–26" DL | 26–28" DL | 28–29" DL | 29–30" DL | 30–31" DL |
|---|---|---|---|---|---|
| 40–50 lb | 600 | 500 | 500 | 400 | 400 |
| 50–55 lb | 500 | 500 | 400 | 400 | 340 |
| 55–60 lb | 500 | 400 | 400 | 340 | 340 |
| 60–65 lb | 400 | 400 | 340 | 340 | 300 |
| 65–70 lb | 400 | 340 | 340 | 300 | 300 |
| 70–75 lb | 340 | 300 | 300 | 250 | 250 |
| 75–80 lb | 300 | 300 | 250 | 250 | 250 |
Adjustment Rules
- Point weight 125 gr: Go one spine stiffer (e.g. 400 → 340)
- Point weight 150 gr+: Go two spines stiffer (e.g. 400 → 300)
- Arrow length 30"+: Go one spine stiffer
- Arrow length under 27": Go one spine weaker
- Mechanical release: Can use recommended spine
- Finger shooting: Go one spine stiffer
Quick rule: When in doubt, go stiffer. A slightly stiff arrow is easier to tune than a weak one, and the performance penalty is smaller. Most pro shops agree: err toward stiff.
Popular Arrow Options by Spine
| Spine | Easton | Gold Tip | Carbon Express | Best For |
|---|---|---|---|---|
| 300 | FMJ 300, Axis 300 | Kinetic Pierce 300 | Maxima Red 300 | Heavy draw, western hunting |
| 340 | Axis 340, FMJ 340 | Hunter Pro 340 | Maxima Red 340 | Most common hunting setup |
| 400 | Axis 400, ST Axis | Traditional 400 | Maxima Blue RZ 400 | Mid draw, whitetail |
| 500 | Axis 500 | Hunter 500 | Predator 500 | Lower draw, youth bows |
| 600 | Jazz 600 | Velocity Pro 600 | Predator 600 | Youth / low draw weight |
Spine vs. Arrow Weight: They're Not the Same
A common mistake is confusing spine with arrow weight (grains per inch or total weight). You can have two arrows with the same spine that weigh very different amounts. For hunting, total arrow weight matters for penetration — aim for 6–8 grains per pound of draw weight (GPP) for ethical kills. A 65 lb bow should be shooting arrows in the 390–520 grain range.
Once you know your arrow weight, you can accurately calculate your sight tape. Enter your draw weight and arrow weight into our sight tape generator — it uses your speed estimate to build exact yardage marks for your slider sight.
Signs Your Spine Is Wrong
- Weak spine: Arrow kicks right for a right-handed shooter, fishtails in flight, inconsistent groups
- Stiff spine: Arrow kicks left for a right-handed shooter, often groups low-left
- Both: Poor paper tune results, tears that won't center regardless of rest adjustment
If you're getting consistent tears in one direction during paper tuning and rest adjustments aren't fixing it, spine is likely the culprit — not form.