So I've got my bow timed and adjusted my lean and every thing. Paper tuned then french tuned then went to bareshaft tune. The other day I was grouping them well and was getting pretty good tail left impacts. I decided to give it a few days and then shoot bare shafts again to see if I was getting the same results and I was. I looked it up and have heard different things about tail left but the most prominent one is the spine is too weak. Im shooting 340 fmj's cut at 27.5".. What do you think about a tail left impact?
Your spine is on the weaker side, but it should be close enough to be ok. I shoot 29.5" @ 70# with 330 spine cut at 29". You could try using 85grain field point and see if that fixes it. If it does go with a stronger spine. But if you were able to paper tune. You should be ok.
Back your tillers out (1) turn and see if you can get it to correct! Different came styles will throw arrows differently! If that doesent help at all I would see if your came has a slight lean to it. IE: 1 yoke tighter on a side then the other :-)
Spine is close to the weaker end. Take two turns out of your limbs to reduce weight and see if that corrects your issue. Thats a sure fire way to see if spine is a problem. Bare shafts can be quite challenging. I can't shoot a bare shaft to save my life past 20 yards, but I can shot 3" inch groups at 60 with fletched arrows all day long. I will usually bare shaft tune to 20 yards and then go to walk back tuning. I figure that its close enough at that point that fletching should be able to easily steer from there.
I just saw on his signature that he is shooting 125gr broad heads. The arrow spine is defiantly to weak.
I could shave a half inch off of my arrow too that would stiffen the spine. I'm going to check it by backing out tiller bolts then if it was a spine issue and not just form I'll tighten them back to 70 lbs then shorten my arrow little by little til it corrects it's self
Another trick is to add weight to the back of the arrow. That stiffens dynamic spine up. I think either way, spine is so close that it might be a bit of an issue unless you drop your weight some. I've always found that broadheads like a slightly stiff spine condition over weak. My current setup is on way on the stiff end of the spine scale on onTarget2 software, but they fly like darts.
I think it is easer to just back off limb bolts, or 85gr fp than to add weight to the back. plus adding weight to the back of the arrow can cause unstable flight.
