August 17, 2021
We have repeatedly heard archers say things like, “I prefer my arrows on the stiff side,” or, “I’d rather my arrows be too stiff than too weak.”
We used to say similar things ourselves, but we’re not so sure this conventional wisdom holds true. One tournament season, one of us found himself stuck between two recommended spines. For years, he shot arrows “on the stiff side.” But, because he was chasing the podium, he wanted to see how both spines would group when shot side by side. He thought the stiffer-spined arrows would win out. Well, not only did the weaker (more flexible) ones group better, he jumped from the middle of the pack to the top of the podium!
As a result, he set out to learn all he could about arrow spine and found there are two kinds: dynamic and static.
The static spine is how each arrow is measured and rated by the manufacturer. This is the spine rating we see in the arrow specs and shafts selection charts. Dynamic spine is how the arrow actually performs when shot from the bow. Although the static spine (stiffness) doesn’t change, dynamic spine (the way the arrow behaves in flight) can change significantly based on factors such as arrow length, point weight, draw weight and draw length.
There are computer programs and apps available that use static spine, arrow length, point weight, bow poundage and draw length to determine dynamic spine. They tell you if your arrows are too stiff or too weak. But while they offer a great starting point, experience tells us they aren’t always accurate at predicting which arrow will fly best.
When our shooter plugged in the two arrows he’d tested, one was stiffer than recommended and the other was weaker. Yet, that “weak” setup shot lights out and put him first in his class.
So, how does this correlate to bowhunting? Many of us shoot fixed-blade broadheads. In the beginning, we had a hard time with the idea of switching to a weaker-spined arrow. It just felt like we needed that extra stiffness for broadhead control. Once again, we were wrong! When we moved to the next weaker arrow spine, we could suddenly shoot more accurately and further than before. In fact, some of us were so “over-spined” with our previous setup we gained 30-40 yards on our effective hunting range!
While searching for the optimum arrow spine for our setups, we discovered that when arrows were too stiff, they would group well 30 yards and under, but as we moved back our groups would open up quite a bit. Conversely, when we shot arrows that were too weak, our groups were pretty solid at long distances, but they never closed up as well as we knew we could shoot at short range. In other words, our accuracy was roughly equivalent at 30 and 60 yards.
The big takeaway is that arrow spine just might be the biggest equipment variable between mediocre accuracy and excellent accuracy. It’s a lot of trial and error, but the results are deadly!