Just wanted to share an arrow build update with all of you.
I have a very long draw length, about 31.5". I also like heavy arrows in that 650gr total weight area because it works for everything in North America and almost everything in Africa. (you can shoot on the shoulder, not just behind the shoulder)
I also have powerful IBO rating bows of 340 and 345 IBO.
I looked at the spine charts and found that I wanted to go with a 200 spine arrow since virtually everyone underspines their arrows. I bought Sirius Archery 200 spine arrows cut carbon length of 31-1/4". I had 180gr insert and collar system. I also use 150gr cut on contact broadheads. Total arrow weight of 646gr.
Bottom line is that the arrows would not paper tune. Even after shimming my bows. Even after moving my rests all the way to the right.
To test this theory, I cranked my 68.5lb draw weight down two rotations of the limb bolts and the tear was still there, but reduced by 60%-70%. I believe this is evidence even a 200 spine was not sufficient due to the significant amount of weight up front on a 200 spine, 646gr, 4mm shaft setup.
I then ignored the paper tuning woes and went outside and bare shaft tuned. I got good bare shaft, vaned, and broadhead flight out to 40 yards. However, accuracy at 8-10 yards was inferior to 20 yards which tells me that the dynamic spine is weak and the arrows haven't stiffened out yet.
***Now the rub***. I discussed this with Sirius Archery and they vehemently disagreed with my opinion on this matter. They thought 200 spine was PLENTY of spine, maybe too much spine, and that both my bows had other defects. I then discussed this with a 4x world champion professional archer and he disagrees with them, it is underspined. He then contacted another famous world champion archer to discuss the matter and he too agreed that it was underspined.
So right now the working theory is that long arrows start to get a very problematic dynamic spine, probably worse because it's 4mm shafts rather than 6mm shafts.
First step I'm taking is that I will be putting wraps on the tail end of my arrow that should reduce FOC slightly and put stiffness on the tail. Second, the arrows will be cut down 1" which removes 11gr from the front. (that was added to the back with the wraps). It is my hope that this resolves the problem. If it does not, I will need to think about what .166" object I can glue into the head of the arrow the strengthen the spine near the front of the arrow modestly to create the same effect as shortening the arrow further.
