Spine question / Mechanical broadband impact

[Hunter24]

Weird question maybe… haven’t seen this addressed in previous posts.

I’ve always read that you, within reason, cannot go too stiff on arrow spine when shooting fixed blade. Does that hold true for mechanicals. I.e can you theoretically get away with a slightly weaker spine with a mechanical?

Also, I’m right in between on all the charts for spine. 29” DL, 74lbs, 27.75” C2C, 175 gr up front, ~470 TAW. Can I get away with 300 spine GT Hunters? With mechanicals? With fixed blades? What if I went up to 79lbs DW? Do you even consider a difference in spine when shooting mechanical vs fixed?

I know I will need to shoot and experiment so just looking for generalities.

Thanks!

 

[RocketRob16]

The big thing about mechanicals from what I’ve seen personally is weight/speed. I started out shooting 387 grain arrows at 317 fps with mechanicals and even on white tails, penetration was poor. At your arrow weight and speed you should have enough energy to be very effective. With mechanicals it’s not a spine issue so I wouldn’t worry about that per se but you do have a significant amount of energy lost when the blades deploy. Make sure your arrows are properly tuned and start sending them down range. You’ll be in good shape.

 

[Billy Goat]

Depending on the head, you might get away with a lighter spine with mechanical head, however it doesn't mean that the arrow is flying true.


The fixed blades basically put vanes on the front of the shaft, so it picks up on imperfections in arrow flight before the drag of the fletching in the rear takes over.


The thing about the drag taking over to correct is its pulling energy from the arrow, and frequently taking a fair distance to straighten out the flight. Sometimes you can see that the arrow still isn't straight by 20 yards, tho it's usually much quicker than that.


Unless it's a 350 ibo bow, you can probably get 300's to tune, but if you go up to 79-80 I'd recommend a stiffer shaft.


The tuning should be the same regardless of broadhead, it's just one style is more forgiving than the other.

 

[Hunter24]

Thanks. That makes sense and jives with what I was thinking. It’s reassuring to hear it from someone with more knowledge/ experience. I’ll shoot em and see how they fly