arrow spine confusion

[vermontrad]

So I am feeling a bit confused. I purchased an arrow test kit from 3 Rivers thinking, hoping, I would see a difference in arrow flight and or grouping. I have a hill tembo 54#@29" (which is my draw length) the arrows are cut to 30" with 160gr field points. I used the 160's 'cause I want to use the hill broadheads and thats what they weight. Anyrate, I saw almost no difference in flight or grouping. I am still learning and my consistency suffers but when I'm off they are ALL off and when I'm on they ALL group together! There are 2 each of 50-55, 55-60, 60-65. What gives?

[aromakr]

Keep in mind the 3 Rivers does not respine the shafts and rely on factory spine, its possible that some of the so called different spines are not different after all! What I would be concerned about is how the shafts group inregard to your point of aim. If you are right handed and they group left of that point then are too stiff, if they group right to the right they are too weak.
Your 60-65 shafts should be the correct spine for a 30" arrow.
Bob

[vermontrad]

Thanks for the input. I have read that to weak a spine would group right and to stiff group left, but they all went to my point of aim. When I was shooting well that is, when I wasn't they randomly scattered all over the target. So, I guess a 50-55 spine and a 55-60spine could both be right at 55 then? Does the distance you shoot from make a differance when testing?

[aromakr]

The spines you received are at 28", when you cut your arrows to 30" they will be 10# less. The proper spine for your setup would be 60-65@28" when cut to 30" they will be 50-54
Bob

[Molson]

Yes it's possible all three shafts combined may only have 5 or 6# difference.

[vermontrad]

Well, I guess a spine tester is in order, This hobby is a tinkers dream! Bob, do you have a notion on how  point weight affects spine? Like going from a 160gr point to a 125gr would change spine by ?.

Thanks for the insights...

[aromakr]

I don't think going down to 125 grains will bother it at all.
Bob

[Orion]

Though there is usually an optimal spine for each bow, most bows will shoot more than one spine well.  I have a number of Hills and generally can vary spine by up to 15# without noticeably affecting arrow flight.  That variance all has to occur on the heavy side of the bow weight at my draw length though.  If I go light, i.e., under the bow's draw weight at my draw length, the arrows don't fly well.

[vermontrad]

HOLY CRAP! I went back out and tried some 65-70# arrows and now the random scattering is gone and they are flyin' where I'm lookin'everytime! OK , there is the occasional flyer, but I'll take that any day over the occasional group! HaHeHeHa....

Maybe now it's time to buy lots of arrows.

Thanks for all you 2 cents!