Arrow Spine, and Weight for Hunting

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For those just getting started with bow hunting, the choice of your hunting Arrow Spine can seem like an overwhelming subject. This report will cover all parts of arrow choice, but in an easy to follow way. We are going to break down the process into several smaller variables before bringing it all together and making a few recommendations.

With the dawn of the compound bow, traditional wood arrows became too dangerous and prone to breaking under the higher forces of a compound bow. This resulted in the creation of aluminum arrows, then finally the more powerful and more lasting carbon arrows that many bow hunters use now. When aluminum arrows were most popular, Easton printed a huge chart to assist hunters and target shooters determine which arrow to select. Each aluminum arrow has a four-digit identifying number printed on the shaft. The first two digits signify the shaft diameter, and the last two represent the wall thickness.

Example: An Easton aluminum arrow with the digits 2512 means the shaft is 0.250″ in diameter with 0.012″ wall thickness.

The Easton arrow graphs were developed only to make it easier for regular shooters to determine what arrow to select for their bow. Since the archery world has moved to carbon arrows, arrow back deflection became the most vital element in searching arrow selection.

Arrow Basics

The key to understanding arrow specifications are easy when you grasp the fundamentals. The arrow back, weight (gpi), and you tip weight are the most significant areas of arrow selection. As soon as you know these things are all interacting with one another, and each has their tradeoffs, the intricate quesiton of arrow section gets much easier.

Arrow Spine

Arrow spine deflection is the trick to the full arrow selection procedure. Spine is how much the shaft bends under a particular load. The standardized evaluation for determining spine deflection is taking a 28″ arrow shaft and hanging a 1.92-pound weight from the shaft midpoint.

Example: Arrows that deflected 0.400 inches were categorized as dimension 400 arrows, and a 0.340″ deflection are a dimension 340 arrow. The smaller the number the stiffer the arrow is.

In regards to shooting these arrows, a 30lb draw bow may barely bend the 340 arrows in any respect. An 80lb bow, on the other hand, would impart higher forces and far more bend to the arrow as if comes off the bow. The quantity of flex directly affects how well the arrow flies as it moves downrange.

Gold Tip Spine Chart: Swing315 fps

Gold Tip Spine Chart: >315 fps


Arrow Weight

The next important specification of carbon arrows is the weight, or GPI (grains per inch). Stiffer arrows will obviously have greater GPI than more flexible arrows. The stiffer shafts have thicker walls, and therefore more stuff, giving them greater grains per inch. Going back to our Spine example arrows, we’re left with a lighter more flexible arrow, and a heavier stiffer arrow. These gaps will come into play later as we get closer to choosing our arrows.

Example: Our 400 size arrow may have a 7.4 GPI, and the 340 arrow a 8.2 GPI. Over a 28 inch arrow shaft, the complete rotating weights become 207 grains and 230 grains respectively.

Tip & Broadhead Weight

The third and last influence in arrow specification is that the weight of your suggestion or broadhead. The heavier the mind, the more weight you’ve got before your bow. More weight in the tip leads to more deflection from the arrow as it leaves the bow. A 125gr broadhead will bend an arrow greater than a 100 grain broadhead on the same shaft. So if you’re shooting a heavier head, you may need an arrow with a bit more spine, depending upon your draw weight. By way of instance, a low draw weight bow using a rigid arrow and hefty tip will lighten up the activity of the arrow. However, the tradeoff is that the arrow will fall must faster. Additional Reading:

  1. Broadheads vs Field Points
  2. Best Broadhead Choices
  3. How to Sharpen Broadheads

Other Factors Influencing Arrow Choice

Now we will need to comprehend the variables on the chemical bow which influence the arrows we will have to choose. Everybody is different and there are many sizes and types of compound bows. However, these factors apply to everybody.

IBO Bow Speed and Cams

IBO is the International Bowhunters Organization, who has archery competitions and developed a benchmark for measuring bow rate. In IBO competition, you’re allowed 5 grain for every pound of bow draw weight. Bow manufacturers typically advertise an IBO bow speed for every version. The rate listed is how quickly the bow can take am arrow weighing 5 grain for every pound of draw weight.

Example: A 70lb draw bow should use an arrow weighing at least 350 grains when shooting in an IBO competition.

Now, a bow rated to take 300 feet per second with a 70% let off will take differently than a bow rated to 360 feet per second with a 90% let off. You’d probably need to use different backbone arrows using these bows. The quicker bow has more aggressive cams, which makes the arrow bend a good deal more as it leaves the bow. When using a mechanical bow launch, the arrow will bend straight down. Whereas a finger drawn bow bends the arrow. This is known as the Archer’s Paradox. On a compound bow, under spined arrows will divert way too much on the discharge, causing the arrow to take badly. You will see this on paper pruning, once the nock is far too high or low in the tip. This is an indication you could require a stiffer arrow.

Draw and Arrow Length

Your draw and total arrow length will help determine the arrow selection also. When using a compound bow. A shorter arrow will bend less than a more arrow and draw span with the identical arrow shaft and tip. Consider it in daily terms, it is logical that a tree that is shorter is more secure than a tall stool using the identical weighted person standing on top of it.


Putting it All Together

The goal now is to maximize the spine and weight of the arrow with the rate of the compound bow. Generally speaking, searching arrow will be a bit heavier and stiffer, with smaller shaft diameters. The cause of this is to create more kinetic energy which could deliver a takedown blow. The smaller diameter shaft has less surface area, and less friction going through the creature, which aides with arrow penetration. An excellent starting point for seekers is to get the complete arrow weight, rotating and broadhead combined, to maintain the 400-grain range.

This is an excellent happy medium for many compound bows. Some shooters can manage up arrows to 500 grain, but that arrow wouldn’t work well on a lower poundage bow. With the heavier arrow, you do not sacrifice precision in the preferred shots from the 20-30 yard range. Rather than bore you or danger confusion with a whole lot of complicated graphs. I will refer you to the shaft selector sites from the top arrow generates. These tools make it super easy to find arrow recommendations based on your bow rate, draw weight, and arrow cut length.

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