Arrow Spine Question

[GreenMachine92]

Hello all,

Does anyone see a problem with shooting a 350 spine 29.5 inch arrow with a 28.5 inch DL @ 75Lbs. IBO 336.

Thanks in advance for the help

 

[Mighty Mouse]

Spine charts/calculators will say you're on the weak side, but they might fly well anyway. How much weight are you putting on the front end?

 

[GreenMachine92]

Spine charts/calculators will say you're on the weak side, but they might fly well anyway. How much weight are you putting on the front end?

Broadhead, insert and collar is 150 grain. 550 grain total arrow weight

 

[GreenMachine92]

Youll be weak, but youll have to shoot them. If they wont tune/group, you have 2" you can lop off of the nock end to stiffen them up.

Thank you!

 

[Mighty Mouse]

Broadhead, insert and collar is 150 grain. 550 grain total arrow weight

You must be shooting a pretty heavy shaft or have a bunch of weight on the back end...or both. Victory XTorsions?

 

[GreenMachine92]

You must be shooting a pretty heavy shaft or have a bunch of weight on the back end...or both. Victory XTorsions?

Yes Xtorsions

 

[Billy Goat]

I don't think you will get that to actually tune.


But it *might* be safe to shoot.

 

[GreenMachine92]

Would you guys recommend 250 or 300 spine?

 

[HbDane]

I’d go 300 spine. I’m a 29” dl with a 28” arrow 72 lb DW. 500gn total weight with 200gn up front. Similar to your specs

 

[Billy Goat]

I shot 75# @ 28.5 DL with around 185 on the front. Think shaft length was about 27.5", I went 250 spine.

Stupid easy to tune.


You can't go too stiff.

 

[Mighty Mouse]

FWIW, here's what qSpine/OT2Go says at 29.5" (top) and 27.5" (bottom) carbon-to-carbon length with 150 gr on the front and 26 gr on the back.

Bow inputs: 336 fps IBO, 75# DW, 28.5" DL, 30" ATA, 6" BH, 80% LO

 

[GreenMachine92]

I'll go with 250 lol

 

[Bump79]

I shot 75# @ 28.5 DL with around 185 on the front. Think shaft length was about 27.5", I went 250 spine.

Stupid easy to tune.


You can't go too stiff.

Yes and no.. I can get a 250 to tune but a 300 groups better. 30" 70# 335 IBO.

 

[Billy Goat]

Yes and no.. I can get a 250 to tune but a 300 groups better. 30" 70# 335 IBO.

What's the difference in weight?


I think a lot of the stiffer spine doesn't shoot as well is actually the difference in weight. Lighter arrows come off the bow faster and are less susceptible to shooter inputs.


I have played with a 50# bow a fair amount testing stiff spine. 300 to 500 spine, I find the biggest difference is weight, not spine. Why do we need flex from a centershot compound?

 

[Bump79]

What's the difference in weight?


I think a lot of the stiffer spine doesn't shoot as well is actually the difference in weight. Lighter arrows come off the bow faster and are less susceptible to shooter inputs.


I have played with a 50# bow a fair amount testing stiff spine. 300 to 500 spine, I find the biggest difference is weight, not spine. Why do we need flex from a centershot compound?

I can't tell you why but I've done it multiple times with matching total arrow weight and not. Generally, the 300's seem to group better. Field points & broadheads. I find faster arrows to be less forgiving and more susceptible to user inputs for hunting purposes.

Dudley & others say the same thing. I do think a stiffer spine is beneficial for hunting purposes though - I might go to a 250 spine for that reason.

 

[GreenMachine92]

You guys are really helpful thats a lot!

 

[stanginthe11s]

Why do we need flex from a centershot compound?

the purpose of flex is to slow the transfer of energy and absorb the shock of the shot cycle. to some degree I believe it also covers up imperfections during the shot. an arrow that is very stiff will be more efficient but also has drawbacks. strings don't always go straight on release so less flex means those oscillations affect the arrow more. that last part is my theory on why stiff arrows don't tune well for some people.

 

[Billy Goat]

I can't tell you why but I've done it multiple times with matching total arrow weight and not. Generally, the 300's seem to group better. Field points & broadheads. I find faster arrows to be less forgiving and more susceptible to user inputs for hunting purposes.

Dudley & others say the same thing. I do think a stiffer spine is beneficial for hunting purposes though - I might go to a 250 spine for that reason.

I have found for myself that it goes against conventional thought. I find stiffer arrow has given me better groups to a point. I think it's a combination of less flex which is easier to control and less individual arrow tuning needed, which is also a factor of less flex.


For a field arrow I use to stay kinda weak, as that was the general advice. I have been going stiffer and the only difference has been easier group tuning of shafts. With a hunting shaft it gets way easier in my opinion.

 

[Billy Goat]

the purpose of flex is to slow the transfer of energy and absorb the shock of the shot cycle. to some degree I believe it also covers up imperfections during the shot. an arrow that is very stiff will be more efficient but also has drawbacks. strings don't always go straight on release so less flex means those oscillations affect the arrow more. that last part is my theory on why stiff arrows don't tune well for some people.

I don't think the arrow flexing a little or a lot is making much difference in shock. If the string isn't dropping consistently, like from face pressure, or a little different release, what's the guarantee that an arrow flexing is going to flex the same with those different inputs? If it's a stiffer arrow you are controlling more of the arrow reaction.


If you have a stiff rest, you might have some benefits to flex. With drop away rests being so popular anymore I don't think we need to have flex in the arrow.

 

[stanginthe11s]

I don't think the arrow flexing a little or a lot is making much difference in shock.

in the big picture, I agree, it probably isn't making a big difference. It does affect the shot cycle though as it changes the transfer of energy through the arrow as well as into the animal. also, the shock I'm referring to is to the arrow or shot cycle, not felt shock.

If the string isn't dropping consistently, like from face pressure, or a little different release, what's the guarantee that an arrow flexing is going to flex the same with those different inputs? If it's a stiffer arrow you are controlling more of the arrow reaction.

I agree, there's no guarantee an arrow will flex the same. my thought was that maybe that normal flex of the arrow also covers up some degree of imperfection, where a stiff arrow doesn't because like you say, we are controlling more of the arrows reaction. I don't really know.

I do know, like you, I also shoot stiff arrows and have accidently grabbed my sons arrows and had almost no difference in grouping. that's between a .300 and a .400 arrow and both arrows are close in weight, about 30gn lighter on the 400's. it was enough to make me think I should have stretched first lol. every arrow tunes different, so if you tune for a 250 then your groups should be the same as the 300 arrows that you initially tuned for.