Great input and a very needed discussion point! One of our members had recently noted in another thread that he couldn't get his broadheads and arrows to fly with any consistency at all.
After reading his thread I assumed it was due to the fact that the arrow shafts for the TAC15's are not spine measured and indexed by the manufacturer, nocks are not aligned to the spine either, so this would likely cause a high level of flight deviation due to the constantly varying spine deflections with each shot.
The typical process used in archery is to tune broadheads to your shafts by setting each broadhead to the exact same position on each shaft so they are all aligned to the same location in relation to the spine of the arrow. This provides a consistency of flight on each arrow.
The member who wrote the thread I'm referring to was suggesting that instead of tuning the broadheads to the shaft, for these arrows he's been doing exactly the reverse and tuning the shafts to the broadheads. He does this by gradually rotating each broadhead until he finds which position will steer the arrow to hit in the same spot as the others at longer distances (60 yards). Not all arrows can be redirected to hit exactly where the ones shot earlier are hitting. In those cases he removes this arrow from his final group.
It's a sorting out and tuning process, but in the end it leaves him with arrows that are good for very tight groups at longer range shots.
The side to side oscillation that you refer to is better known as the Archers Paradox. I'm not sure if the oscillation on these arrows follows that typically seen on other shafts for a number of reasons.
- These arrows are much longer than any other crossbow bolts.
- The new type of Carbon Filament Woven Fibers used in their construction have entirely different spine and flex points than any arrow that's come before these and are not similar in design to any other arrow ever made.
- The Spine Deflection readings and characteristics are unique and are unpublished, which is why PSE had special vane configurations created to provide optimal flight performance.
- All flight testing and data was developed for the 85 gram field points. Broadheads were tested later, but were not the basis for the shaft development matrix.
Can you provide any input or feedback on how your performance is when shooting at longer distances such as between 60 and 100 yards?
We have been testing and searching for ways to improve the accuracy at these distances and we now understand a good bit about the information I've outlined above. Don't get me wrong, these crossbows are very accurate compared to others, but we are looking for 3" groups at 100 yards and that's entirely possible if we can find a way to make each shaft fly the same as the one before it. It's already possible if you shoot the same arrow each time, but as soon as you change to a different shaft, you lose the accuracy.
I think many members would stand to gain a great deal if you've been able to overcome any of these issues and can assist us with any ideas on how resolving these problems can best be accomplished?
It's clear that you have a great knowledge base on crossbow properties and performance, so it's great having you on the team.
Thank you for sharing your knowledge with us on this thread. Please keep it coming, since there's so much to still learn and discover.