Compound Bow Arrow Size 340 vs 400: Which Is Best for You?

Choosing the right arrow size for your compound bow can feel confusing, especially when you see numbers like 340 and 400. These numbers are not the length or weight of the arrow, they represent spine rating, which is all about how much the arrow bends when shot. Picking between 340 vs 400 spine arrows is a key decision for accuracy, safety, and performance. If you’re new to archery, or even if you’ve shot before, understanding these numbers can help you shoot straighter and safer.

Let’s explore what the spine rating means, how 340 and 400 arrows perform differently, and why the choice matters. We’ll cover every practical angle, from physics to hunting tips, and even how different bows and draw weights affect your choice.

By the end, you’ll know exactly which arrow is right for your setup.

What Is Arrow Spine?

The arrow spine describes how much an arrow bends when force is applied. The number comes from a test: a 28-inch arrow is supported at each end, then a weight is hung in the middle. The amount it bends (measured in thousandths of an inch) is the spine. A 340 spine arrow bends 0.340 inches; a 400 spine arrow bends 0.400 inches.

A lower number means a stiffer arrow, it bends less. A higher number means a softer arrow, it bends more. This matters because the arrow has to flex just right when shot, or it won’t fly straight.

Why Arrow Spine Matters

If your arrow is too stiff or too soft for your bow, it won’t fly accurately. It can even be dangerous. The right spine ensures the arrow leaves your bow safely and hits where you aim.

• Too stiff (low spine number): Arrow won’t flex enough, may fly off target.
• Too soft (high spine number): Arrow flexes too much, can hit the bow riser or miss the mark.

Arrow spine is affected by:

• Bow draw weight
• Arrow length
• Arrow point weight
• Arrow material

Compound Bow Arrow Size: 340 Vs 400

These two arrow sizes are among the most common for compound bows. Let’s break down their differences and when to use each.

340 Spine Arrow

A 340 spine arrow is stiffer. It is best for:

• Heavy draw weight bows (60, 75 lbs)
• Long arrows (over 29 inches)
• Heavier tips (over 125 grains)
• Hunters using broadheads

400 Spine Arrow

A 400 spine arrow is more flexible. It works well for:

• Medium draw weight bows (40, 60 lbs)
• Shorter arrows (26, 29 inches)
• Standard tips (100, 125 grains)
• Target shooters

How To Choose Between 340 And 400 Spine Arrows

Choosing the right arrow is not just about the number. You need to consider your bow, your shooting style, and your goals.

1. Bow Draw Weight

Draw weight is the force needed to pull the bowstring back. Heavier bows require stiffer arrows.

• Bows over 60 lbs: Choose 340 spine
• Bows 40, 60 lbs: Choose 400 spine

2. Arrow Length

Longer arrows flex more. If your arrows are longer, you need a stiffer spine.

• Arrows over 29 inches: 340 spine
• Arrows 26, 29 inches: 400 spine

3. Arrow Point Weight

Heavier tips make arrows flex more.

• Tips over 125 grains: 340 spine
• Tips 100, 125 grains: 400 spine

4. Arrow Material

Carbon arrows are stiffer than aluminum. If you use carbon arrows, you may need a lower spine number.

5. Shooting Style

Hunters often use stiffer arrows for broadheads; target shooters can use softer arrows.

Real-world Example

When I tested both sizes with my 65 lb compound bow, the 340 spine arrow shot much straighter at longer distances. The 400 spine arrow flexed too much, causing the arrow to drift. With a lighter bow (50 lbs), the 400 spine was more accurate.

Comparison Table: 340 Vs 400 Spine Arrows

Here’s a simple comparison:

340 Spine Arrow: Detailed Guide

Who Should Use 340 Spine Arrows?

If you shoot a heavy compound bow (draw weight above 60 lbs), you need a stiffer arrow. The 340 spine handles the force without bending too much.

Benefits Of 340 Spine Arrows

• Better accuracy with heavy bows
• Safer for high-energy shots
• Works with heavy broadheads

Downsides

• May be too stiff for lighter bows
• Can reduce arrow speed if paired with low draw weight

Practical Advisor Tip

Pro Tip: If you shoot broadheads, always choose a stiffer arrow. Broadheads create more force and need less flex.

Example Situations

• Bowhunting large game: Elk, deer, bear
• Shooting at long distances (50+ yards)
• Using arrows longer than 29 inches

400 Spine Arrow: Detailed Guide

Who Should Use 400 Spine Arrows?

These arrows are perfect for medium draw weight bows (40, 60 lbs). Target shooters and hunters with lighter setups often prefer them.

Benefits Of 400 Spine Arrows

• Higher arrow speed
• Good for lighter bows
• Lower cost

Downsides

• Too flexible for heavy bows
• Can bend too much with heavy tips

Practical Advisor Tip

Pro Tip: For target shooting under 40 yards, a 400 spine arrow gives a flatter trajectory and is easier to tune.

Example Situations

• Target archery with 50 lb bow
• Hunting small game with standard tips
• Shooting arrows shorter than 29 inches

Arrow Performance: Factors That Matter

Arrow spine is just one part of the equation. Here are other factors that affect performance:

• Fletching type (vanes vs feathers)
• Arrow weight
• Bow tuning
• Arrow rest position

If you change any of these, you may need to adjust your arrow spine.

Data Table: Arrow Spine Selection Based On Bow Specs

Use this reference to match your bow specs with the right spine:

Common Mistakes When Selecting Arrow Spine

• Ignoring draw weight: Using a flexible arrow with a heavy bow can cause dangerous misfires.
• Wrong arrow length: Longer arrows need stiffer spine, but many shooters forget this.
• Using heavy tips with soft spine: This makes arrows flex too much, leading to poor accuracy.
• Not tuning bow: Even the right spine won’t work if your bow isn’t tuned.

How To Test Arrow Spine

You can test if your arrow spine is right by shooting paper tuning. Shoot an arrow through a sheet of paper at close range. If the arrow tears the paper cleanly, your spine is correct. If it tears sideways, your spine may be wrong.

When To Upgrade Arrow Spine

If you change your bow’s draw weight, arrow length, or tip weight, you may need to upgrade your arrows. Always check spine charts when you adjust your setup.

340 Vs 400: Arrow Speed And Penetration

Stiffer arrows (340) usually have less speed but more penetration. Flexible arrows (400) fly faster but may not penetrate as deeply.

• 340 spine: More penetration, less speed
• 400 spine: More speed, less penetration

Example: For hunting, penetration is more important. For target shooting, speed and flat trajectory matter more.

Arrow Spine For Broadheads Vs Field Points

Broadheads require stiffer arrows. Field points can use softer arrows.

• Broadheads: Use 340 spine for heavy bows
• Field points: 400 spine is fine for medium bows

How Arrow Spine Affects Accuracy

If your spine is wrong, arrows will not group well. Shots will drift left or right. Correct spine gives tighter groups and better accuracy.

Credit: www.huntersfriend.com

Data Table: Accuracy Comparison

Non-obvious Insights

Many beginners think arrow length is not important, but it plays a big role in spine selection. Also, the tip weight can change spine needs, a heavier tip always needs a stiffer spine. Most archery shops will help you measure your arrow length and suggest the right spine.

Safety Warnings

Warning: Using the wrong spine with a heavy compound bow can cause arrows to break or fly unpredictably. Always check manufacturer charts.

Tuning Tips

If your arrows are flying erratically, try a stiffer or softer spine. Small changes in tip weight or arrow length can affect performance.

Arrow Brands And Spine Ratings

Different brands rate their arrows slightly differently. Always check the brand’s spine chart. For example, Easton and Gold Tip have different standards.

Recommended Resources

For more details on arrow spine and selection, check the official Easton arrow chart at Easton Archery.

Frequently Asked Questions

What Happens If I Use A 400 Spine Arrow With A Heavy Compound Bow?

If you use a 400 spine arrow with a bow over 60 lbs draw weight, the arrow will flex too much. This can cause poor accuracy and may even damage the arrow. The arrow could hit the bow riser, resulting in dangerous situations.

Can I Use 340 Spine Arrows For Target Shooting?

Yes, but only if your bow’s draw weight is high. If your bow is below 60 lbs, the 340 spine may be too stiff, causing the arrow to fly off-target. For bows under 60 lbs, a 400 spine arrow is usually better for target shooting.

How Does Tip Weight Affect Spine Selection?

Heavier tips increase arrow flex. If you use tips heavier than 125 grains, you need a stiffer arrow (lower spine number). This helps the arrow recover and fly straight after being shot.

How Do I Measure My Arrow Length For Spine Selection?

Measure your arrow from the nock groove to the end of the shaft (not including the tip). Use this length when checking spine charts. Longer arrows need a stiffer spine.

What Is The Best Arrow Spine For Beginners?

If you’re new to compound bows and have a medium draw weight (40, 60 lbs), start with 400 spine arrows. They are easier to tune and more forgiving for beginners.

Choosing between 340 vs 400 spine arrows is a key step for compound bow shooters. By understanding your bow’s draw weight, arrow length, and tip weight, you can pick the right arrow for accuracy and safety. Testing your setup and tuning your bow makes a big difference. Remember, the right arrow spine not only helps you shoot better, it keeps you safe. If you have doubts, consult an archery expert or use trusted charts from major brands. With practice and the right arrow, your shots will be straighter and your experience much better.