Arrow spine is the single most important arrow specification you'll ever choose. Get it wrong and no amount of tuning fixes your accuracy — the arrow is fighting the bow from the moment it leaves the rest. Get it right and everything else falls into place: groups tighten, broadheads fly true, and the bow tunes cleanly.
Most spine resources online are thin. They show a basic compound bow chart and call it done. This guide goes further: compound and recurve charts, manufacturer naming conventions decoded, dynamic spine adjustments, how FOC interacts with spine, and a visual diagnostic for reading exactly what your arrows are doing wrong. If you've been confused about spine before, this is the resource that ends that.
If you want the quick interactive version for compound bows, see our arrow spine chart tool. If you want to understand the fundamentals first, start with our arrow spine selection guide. This post covers everything the others don't.
Contents
Static Spine vs. Dynamic Spine
There are two ways to measure arrow stiffness, and conflating them causes real confusion.
Static Spine
Static spine is the standardized lab measurement. The AMO/ATA method hangs a 1.94 lb weight from the center of a 29-inch arrow supported at both ends, then measures the deflection in inches. That deflection number is the spine: a 400 spine bends 0.400 inches, a 300 spine bends 0.300 inches. Lower number = stiffer arrow. This is the number printed on the shaft and used in all the charts below.
Dynamic Spine
Dynamic spine is how the arrow actually behaves when it's shot from your specific bow. It's influenced by everything static spine isn't: your draw weight, your draw length, the point weight on the front of the arrow, arrow length, and whether you're shooting fingers or a mechanical release. An arrow that measures 400 static might behave like a 340 or a 500 depending on your setup.
This distinction matters because two archers can shoot the same 400 spine arrow and get completely different results. A 70 lb compound shooter at 29" gets weak flight. A 50 lb recurve shooter at 27" gets stiff flight. The static measurement is the starting point — dynamic factors determine whether that starting point is right for your rig.
The practical takeaway: Always choose your arrow based on your dynamic spine requirements. Use the static spine number as the label, then adjust for your actual shooting conditions using the rules in the dynamic adjustments section below.
Compound Bow Spine Chart
The table below covers the most common compound bow setups with 100 grain and 125 grain point weights. Base draw length is 28 inches — see the dynamic adjustments section for longer or shorter arrows. For the full interactive version, see our arrow spine chart.
100 Grain Point Weight
| Draw Weight | 24–25" Arrow | 26–27" Arrow | 27–28" Arrow | 28–29" Arrow | 29–30" Arrow | 30–31" Arrow |
|---|---|---|---|---|---|---|
| 40–45 lb | 600 | 600 | 500 | 500 | 400 | 400 |
| 45–50 lb | 600 | 500 | 500 | 400 | 400 | 340 |
| 50–55 lb | 500 | 500 | 400 | 400 | 340 | 340 |
| 55–60 lb | 500 | 400 | 400 | 340 | 340 | 300 |
| 60–65 lb | 400 | 400 | 340 | 340 | 300 | 300 |
| 65–70 lb | 400 | 340 | 340 | 300 | 300 | 250 |
| 70–75 lb | 340 | 300 | 300 | 250 | 250 | 250 |
| 75–80 lb | 300 | 300 | 250 | 250 | 250 | 250 |
125 Grain Point Weight
Heavier points make the arrow act weaker. Shift one spine stiffer across the board compared to the 100 grain chart above. The table below does that for you.
| Draw Weight | 24–25" Arrow | 26–27" Arrow | 27–28" Arrow | 28–29" Arrow | 29–30" Arrow | 30–31" Arrow |
|---|---|---|---|---|---|---|
| 40–45 lb | 500 | 500 | 400 | 400 | 340 | 340 |
| 45–50 lb | 500 | 400 | 400 | 340 | 340 | 300 |
| 50–55 lb | 400 | 400 | 340 | 340 | 300 | 300 |
| 55–60 lb | 400 | 340 | 340 | 300 | 300 | 250 |
| 60–65 lb | 340 | 340 | 300 | 300 | 250 | 250 |
| 65–70 lb | 340 | 300 | 300 | 250 | 250 | 250 |
| 70–75 lb | 300 | 250 | 250 | 250 | 250 | 250 |
| 75–80 lb | 250 | 250 | 250 | 250 | 250 | 250 |
Highlighted rows (60–70 lb) represent the most common hunting setups in North America. If you're in that range, 340 spine at 28–29" is your default starting point — it suits the majority of whitetail and elk hunters.
Recurve & Traditional Bow Spine Chart
Recurve and traditional longbow shooters are almost completely ignored by online spine resources. That's a problem, because recurve spine selection is meaningfully different from compound selection — and getting it wrong on a recurve is arguably worse, since you don't have the let-off and cams to help compensate.
How Recurve Spine Selection Differs
Recurves are shot with fingers, not a mechanical release. Fingers grip the string across three points, which pushes the arrow sideways at release — a much more aggressive launch than the clean single-point release from a compound trigger. The result: recurve archers need to account for the "archer's paradox" more carefully, and arrows generally need to be stiffer relative to draw weight than a compound shooter would need.
The AMO recurve method works from your actual draw length and the bow's measured draw weight at your draw length — not the manufacturer's marked peak weight, which is typically measured at 28 inches. If you pull a 45 lb recurve to 30 inches, you're actually pulling closer to 50 lb. That's the number you use.
Recurve Spine Chart — AMO Method
Chart assumes a 28-inch draw length with a standard 100 grain field point. Standard aluminum or carbon arrows. Finger shooting.
| Actual Draw Weight at Your DL | 25" Arrow | 26" Arrow | 27" Arrow | 28" Arrow | 29" Arrow | 30" Arrow |
|---|---|---|---|---|---|---|
| 20–25 lb | 1000 | 1000 | 800 | 800 | 700 | 700 |
| 25–30 lb | 800 | 800 | 700 | 700 | 600 | 600 |
| 30–35 lb | 700 | 700 | 600 | 600 | 500 | 500 |
| 35–40 lb | 700 | 600 | 600 | 500 | 500 | 500 |
| 40–45 lb | 600 | 600 | 500 | 500 | 500 | 400 |
| 45–50 lb | 600 | 500 | 500 | 500 | 400 | 400 |
| 50–55 lb | 500 | 500 | 500 | 400 | 400 | 340 |
| 55–60 lb | 500 | 400 | 400 | 400 | 340 | 340 |
| 60–65 lb | 400 | 400 | 340 | 340 | 300 | 300 |
Practical example: You shoot a recurve marked 45 lb @ 28". Your actual draw length is 29.5". At that extra draw length, you're pulling approximately 49–50 lb. You're shooting a 29" arrow with a 100 grain point. The chart says 400 spine. That's your starting point — tune from there with a bare-shaft test or paper tuning.
Longbow Adjustments
Longbows have a narrower, more rigid riser than recurves, and many traditional longbow archers shoot off the shelf with no elevated rest. Both factors increase the effective flex on the arrow. As a rule: take your recurve spine selection and go one step stiffer (lower number). A recurve result of 500 means a longbow shooter should test 400 first.
Recurve Arrow Material Notes
- Carbon arrows (most modern recurve hunters): Use the chart above directly. Carbon arrows maintain consistent spine regardless of temperature.
- Aluminum arrows: The chart works, but aluminum deforms on impact and can develop a set (permanent bend) over time. Spin-test regularly.
- Wood arrows (traditional only): Wood spine varies by species, grain, and moisture. Use the chart as a baseline but expect to group-tune by hand — wood arrows rarely come in tight enough tolerances to rely solely on the chart.
Manufacturer Spine Naming Conventions
Here's where a lot of archers get tripped up: not every brand labels spine the same way. Some use the AMO deflection number directly (340, 400, 500). Others use marketing names that map to those numbers but aren't immediately obvious. The table below decodes the most common systems.
| Equivalent Spine | Easton | Gold Tip | Carbon Express | Black Eagle | Notes |
|---|---|---|---|---|---|
| 250 (stiffest) | FMJ 250, Axis Long Range 250 | Kinetic Pierce 250 | Maxima Red 250 | Rampage 250 | For high poundage / short arrows |
| 300 | FMJ 300, Axis 300 | Kinetic Pierce 300, Hunter Pro 300 | Maxima Red 300, Maxima Triad 300 | Rampage 300, Spartan 300 | Heavy setups, western hunting |
| 340 | FMJ 340, Axis 340, ST Axis 340 | Hunter Pro 340, Pierce Platinum 340 | Maxima Red 340, Maxima BLU RZ 340 | Rampage 340, Spartan 340 | Most popular hunting spine |
| 400 | Axis 400, ST Axis 400, Sonic 400 | Hunter XT 400, Traditional 400 | Maxima Blue RZ 400, Predator II 400 | Carnivore 400, Spartan 400 | Mid-weight compound, recurve heavy |
| 500 | Axis 500, Sonic 500, Injexion 500 | Hunter 500, Velocity Pro 500 | Predator 500, Heritage 500 | Carnivore 500, Outlaw 500 | Light compound, recurve medium |
| 600 | Jazz 600, Sonic 600 | Velocity Pro 600, Hunter 600 | Predator 600, Heritage 600 | Carnivore 600 | Youth / low draw / recurve light |
| 700–1000 | Jazz 700, Gamegetter | Velocity 700+ | Heritage 700+ | Carnivore 700+ | Light recurve, traditional, youth |
Carbon Express Dual Spine Technology
Carbon Express Maxima arrows use a dual-zone construction — the middle of the shaft is stiffer, and the front and rear sections are more flexible. The spine number they print (e.g., 350, 250) doesn't map cleanly to the AMO standard because the stiffness isn't uniform along the length. Their charts are tuned specifically for their own arrows, so always use the Carbon Express selection chart for Maxima shafts rather than a generic chart.
Black Eagle's ".300" vs "300" Labeling
Black Eagle occasionally labels spines with a decimal (e.g., ".300") in their literature, which is simply the deflection in inches with the decimal shown explicitly. It's the same as saying "300 spine." Don't let the formatting throw you off — a Black Eagle Rampage .300 and an Easton FMJ 300 are targeting the same stiffness range.
Dynamic Spine Adjustments
Once you have a starting spine from the chart, apply these adjustments to arrive at your actual recommended spine. Each factor below changes how stiff or weak the arrow behaves in flight — independently of what the shaft is labeled.
- Heavier point weight (125 gr instead of 100 gr): Spine acts weaker — go one step stiffer (e.g., 400 → 340)
- Very heavy point weight (150 gr+): Spine acts significantly weaker — go two steps stiffer (e.g., 400 → 300)
- Lighter point weight (under 75 gr): Spine acts stiffer — go one step weaker (e.g., 340 → 400)
- Longer arrow (every +1" over 28"): Arrow acts weaker — go one step stiffer per 2" added
- Shorter arrow (every -1" under 27"): Arrow acts stiffer — go one step weaker per 2" removed
- Higher draw weight (every +10 lb): Need stiffer spine — move one step down the chart
- Mechanical release (compound): Use the chart recommendation directly — clean release adds no side pressure
- Finger shooting (recurve, traditional, or compound): Go one step stiffer vs. chart — fingers apply lateral force at release
- Below-center rest (shelf or low rest): Slightly increases effective flex — go one step stiffer if symptoms appear
- Very aggressive cam (high let-off, aggressive roll-over): Can add cam timing kick — go one step stiffer if tuning is stubborn
When in doubt, go stiffer. A slightly overspined arrow is far easier to tune than an underspined one. You can move a stiff arrow into tune with rest adjustment. A weak arrow requires a shaft change. Most pro shop techs will tell you the same thing: when you're on the border between two spine ratings, buy the stiffer one.
FOC and Spine — How They Interact
Front-of-center (FOC) percentage describes how much of your arrow's total weight sits in the front half of the shaft. Standard hunting FOC is 10–15%. Heavy-FOC setups used by some elk and bear hunters run 17–25% or even higher.
Here's the relationship that matters: high FOC acts like weak spine. When you add weight to the front of the arrow — heavier inserts, heavy field points, or oversized broadheads — you're increasing dynamic flex at the front of the shaft. The arrow bends more during the power stroke. This is the same effect as moving to a weaker spine shaft. A 400 spine arrow with a 200 grain brass insert and 125 grain broadhead may be behaving like a 500 spine. If you've dialed up FOC and your arrows are fishtailing or paper tuning won't center, your spine is now too weak for the new configuration — go one or two steps stiffer before you adjust anything else.
The reverse is also true: if you switch from 125 grain broadheads to 75 grain mechanicals, you've effectively made the arrow stiffer. Groups that were centered may shift. Run a fresh paper tune any time you change point weight. For a thorough FOC calculation and to understand exactly where your current setup sits, use our FOC Calculator.
Signs Your Spine Is Wrong — Visual Diagnostics
Before you blame your form, your rest, your peep, or your sight, check your spine. Bad spine produces consistent, repeatable patterns that form issues don't. If your misses look the same every time regardless of hold, your arrows are talking to you.
Weak Spine Symptoms
- Right-hand shooter: arrows hit left of point-of-aim consistently
- Left-hand shooter: arrows hit right of point-of-aim consistently
- Visible fishtailing or porpoising in flight
- Paper tune shows a right tear (right-hand shooter)
- Broadheads impact significantly left of field points
- Groups are vertical ovals, not circles
- Walk-back tuning shows point-of-impact drifting steadily as distance increases
- Increased arrow noise in flight
Stiff Spine Symptoms
- Right-hand shooter: arrows hit right of point-of-aim consistently
- Left-hand shooter: arrows hit left of point-of-aim consistently
- Paper tune shows a left tear (right-hand shooter)
- Broadheads impact right of field points (right-hand shooter)
- Poor groups that aren't fixed by rest left-right adjustment
- Arrows hit lower than expected even at closer distances
- Walk-back tuning shows point-of-impact drifting opposite direction from weak
- Arrow feels "stiff" against rest at release — clipping sound
How to Confirm It's Spine and Not Form
Shoot five arrows at 20 yards. If they group tightly but in the wrong place, it's likely spine or rest position — not form. Form issues show up as scattered groups. If you have a tight group that moves consistently left or right, and rest adjustment doesn't move the group proportionally, spine is the problem. Confirm with a bare-shaft test: shoot a fletched arrow and an unfletched shaft at 10 yards. If the bare shaft hits clearly left or right of the fletched arrow, your spine needs adjustment.