There have been several questions about tuning and spine recently. There always are really, but it's getting close to the season openers so people are shooting more I think.
I was out today bare shaft tuning my bow with some new arrows. Since everyone is always asking about spine and how to bare shaft tune or broad head tune I thought I would share my experiences on the subject and show you a little test I did.
This is a picture of some groups I shot today. The yellow fletched arrows are 27 inch 2213 arrows with 100 grn tips and blazer 2" vanes. According to my OnTarget program these spine perfect at 53-54 lbs for my bow. I actually had to increase my draw weight to get them perfect though. I guess I'm going to have to calibrate the program to my set up. It was pretty close though. It showed them being slightly stiff for 53 lbs and slightly weak for 60 lbs.
The Orange nock feather fletched arrows are the same shafts and tips cut to 24 inches (I have a 26 inch draw length). The 27 inch arrows were shot at 30 yards, two fletched, one bare shaft (middle one). The 24 inch arrows were shot at 20 yards. I didn't trust bare shafting them at 30 yards.
As you can see the correct spine really pays off. I am normally one to suggest a stiffer spine arrow, however this goes to show that too stiff isn't always that great either. I will add that I have gotten severely stiff arrows to bare shaft and shoot broad heads well. It depends on the arrow, type of fletch and amount of FOC. And the broad head I guess.
I shot Arrow Dynamics Nitro Stingers for a while and they spined up to 100 lbs. I was shooting them out of a 50 lb bow at 24 inches with 85 grn tips. They flew well enough that I cut an arrow in half at 30 yards when broad head tuning. Don't shoot your field tipped arrows first, it gets expensive
. If all I did was hunt these would be my arrows of choice hands down.
Here is another pic of some groups I shot last year.
The red vaned arrows are 25 inch 2213's with 100 grn tips, but I put a length of 2016 shaft inside them (fits perfect) to get the weight up to 450 grns. I don't have a clue what they spine, but they bare shafted well for me. The feather fletched purple arrows are 24 or 23 inch easton jazz 1816's with 80 grain glue in target points (no inserts). I would say the 2213 were a bit stiff and the 1816's were way weak. I also don't remember what distance this was, probably 20 or 30 yards.
They grouped well, but as you can see the impact points shifted from one spine to the other. I bet if I would have tried to bare shaft the lighter arrows it wouldn't even have hit the target. And I sure wouldn't want to shoot a broad head on one! I will note that I got the 1816's to paper tune and shoot bullet holes out of this set up. That is why I feel paper tuning is good for checking your initial nock point and centershot. Beyond that though I don't have much use for it to be honest. It is also a good way to check your grip. If you torque the bow a lot it will show up when you paper tune.
In both these pics I was shooting at the same spot for both groups in order to show the difference in impact points and grouping. I did a simular test a month or so ago at 70 yards but lost the picture
. At that distance the better spine and bow tune made a large difference in groups.
I feel you would see simular results either with bare shafts or broad heads. Not exact, but the differences would be evident in one form or another.
My tuning session today shows why I normally base my new set ups on the mid draw weight range of a bow. And why I try to shoot a bow at the middle or lower draw weight range. When using a new set up it gives some leeway to play with the draw weight of your bow to match the spine better. I may switch to a heavier tip, or next time I get arrows cut them an inch or so longer so I can drop my weight back down.
I hope this helps someone.
Paul