Arrow question?

[CoHiCntry]

I recently got some new arrows from the archery shop. I usually just let them take care of things since I'm no genius when it comes to archery tackle. I've been shooting/ hunting archery for around 10 years now. Some years I don't even archery hunt, it really all depends on the tags I draw. I also hunt with rifle and muzzleloader. Haven't archery hunted for a couple years now. So here's my question...

I've got a 27" draw, shooting 400 spine arrows with a 100 gr tip. I was thinking about going with a 125 gr broad head to increase the over all weight of my arrow knowing it's on the lighter side. I looked at a chart on-line and it looked like I would possibly be under spined if I moved up in broad head weight? Or at least right on the bubble.

Got me thinking... I hear "under spined" all the time but not really "over spined". Is there such a thing? If so what are the down falls to being over spined? I was thinking I could go to a 340 spine which would work better with the 125 broad head? Although, 400 spine seems to be recommended for my draw length. Thoughts???

 

[bowrunner]

I recently got some new arrows from the archery shop. I usually just let them take care of things since I'm no genius when it comes to archery tackle. I've been shooting/ hunting archery for around 10 years now. Some years I don't even archery hunt, it really all depends on the tags I draw. I also hunt with rifle and muzzleloader. Haven't archery hunted for a couple years now. So here's my question...

I've got a 27" draw, shooting 400 spine arrows with a 100 gr tip. I was thinking about going with a 125 gr broad head to increase the over all weight of my arrow knowing it's on the lighter side. I looked at a chart on-line and it looked like I would possibly be under spined if I moved up in broad head weight? Or at least right on the bubble.

Got me thinking... I hear "under spined" all the time but not really "over spined". Is there such a thing? If so what are the down falls to being over spined? I was thinking I could go to a 340 spine which would work better with the 125 broad head? Although, 400 spine seems to be recommended for my draw length. Thoughts???

If you are on the line, you should for sure bump up in spine. In my experience, you are better off to go a little over spine than be under spined. To answer your question about being over spined, Im sure you can, but I never have been.

A stiffer arrow will tune better than an under spined arrow out of most compound bows.

I bet a 340 shaft with your setup would shoot good. You could even put in a heavier insert and keep your 100gr heads if you want.

 

[dirtclod Az.]

I shoot 340 with 125gr. heads works great except in wind.Never tried anything stiffer or heavier.Just hunt stink pigs and Muleys.

 

[tdcour]

I'd go with the 340. I have a 28" draw and 70# draw weight and shoot a 340 FMJ cut to 27", which is pretty short and makes the arrow act more stiff. I put a 50 grain insert inside and shoot a 100 gr broadhead. I have no issues tuning my arrows and broadheads, but it does seem like the stiffer arrows are a little less forgiving.

 

[bowrunner]

I shoot Easton axis 300s with 50gr of brass and 100gr heads, so its similar to tdcour. My arrows are 28.5" long and I shoot 68lbs for comparison.

 

[Slugz]

Whats your FOC ? I know in the hunting world we say 10 to 15% is a good range. I tend to have it at the higher end at 14%.

Higher will give you better stability but nose dive quicker......lower will be better flight path but eratic flight.

I think its important to also fold that into the spline discussion.

 

[CoHiCntry]

I’m not sure on FOC. I need to check it.

Here’s another question... if I’m shooting a 400 spine arrow, which is 400 @ 28” correct? If it was cut to 27” would it actually be more like a 385 spine? Just doing the math, that’s what I come up with. Is it that simple or is there more to it?

 

[bowrunner]

I’m not sure on FOC. I need to check it.

Here’s another question... if I’m shooting a 400 spine arrow, which is 400 @ 28” correct? If it was cut to 27” would it actually be more like a 385 spine? Just doing the math, that’s what I come up with. Is it that simple or is there more to it?

I think you are on the right track. It is the deflection at that distance for a certain weight. I don't know if it is quite that simple of math. Deflection is calculated with PL^3/48EI in this case.... so the length is cubed.... so just a rough calculation... maybe... 358spine.

 

[bowrunner]

fyi, The 358 spine that I calculated would be the 28" long equivalent to your poundage. I think.

 

[tdcour]

Not sure on the exact calculations, but yes, you would be going stiffer. Never thought to actually calculate the stiffness change though. I'd be interested to see how stiff my arrows are with the shorter length then the heavy weight up front. Heck, maybe they stay the same and offset each other.

 

[bowrunner]

Yea I don't know if that is the way to do it or not. I just follow the Easton chart for my axis arrows and have had good luck. I was shooting Easton epic 340s at 28.75" long with regular inserts and 100gr heads and about 68lb and they were slightly weak. I switched to Easton axis 300s with 50 gr brass inserts and 100 gr heads and they fly very good. So I went up a size in spine, but reduced the spine some by adding heavier weight up front.

 

[CoHiCntry]

Thanks for all the input so far... I checked the FOC and I'm getting 10.7%. That's with a field point and not a broad head though. So obviously that will change. I was just curious what it was now. My arrow as it sits is only at 370 grains. I'd like to get it a little heavier but am still concerned that adding too much weight will cause me to be under spined with a 400 shaft. Guess I'll find out!

 

[bowrunner]

Thanks for all the input so far... I checked the FOC and I'm getting 10.7%. That's with a field point and not a broad head though. So obviously that will change. I was just curious what it was now. My arrow as it sits is only at 370 grains. I'd like to get it a little heavier but am still concerned that adding too much weight will cause me to be under spined with a 400 shaft. Guess I'll find out!

Keep us posted!

 

[tdcour]

Depending on how comfortable you are with a shorter arrow, you could always trim an inch off, then add more tip weight. Not sure if they completely even themselves out, but I'm at 501 grains with a 27" FMJ. I use a 100 gr head with a 50 gr insert on arrows cut to 27" even though I'm a 28" draw. Not much room between the rest and the bh, but it has been working for me.

 

[Slugz]

Thanks for all the input so far... I checked the FOC and I'm getting 10.7%. That's with a field point and not a broad head though. So obviously that will change. I was just curious what it was now. My arrow as it sits is only at 370 grains. I'd like to get it a little heavier but am still concerned that adding too much weight will cause me to be under spined with a 400 shaft. Guess I'll find out!

If this is a dumb question or I missed something in your post then forgive me. Do you shoot all year with a different size field point than your broad head ?

 

[bowrunner]

I can’t answer for CoHiCtry, but I know if you shoot a longer broadhead, the balance point will be slightly further forward than a field point. I think that difference is pretty small, but it is measurable.

 

[CoHiCntry]

If this is a dumb question or I missed something in your post then forgive me. Do you shoot all year with a different size field point than your broad head ?

No, I'm currently using a 100 gr field point. As bow runner mentioned, a broad head will be a little longer than the field point so that would change the over all length and balance point slightly when figuring FOC. Probably wouldn't be a bunch though...

 

[Slugz]

No, I'm currently using a 100 gr field point. As bow runner mentioned, a broad head will be a little longer than the field point so that would change the over all length and balance point slightly when figuring FOC. Probably wouldn't be a bunch though...

Agree.

After rereading I'm not sure where I got the idea you were hunting with 125g broad heads and practicing with 100gr points during the year. Disregard.

 

[CoHiCntry]

Agree.

After rereading I'm not sure where I got the idea you were hunting with 125g broad heads and practicing with 100gr points during the year. Disregard.

No problem. I am wanting to switch to a 125 grain broadhead to increase the weight of my arrow. I’m still concerned that with a 400 spine I will be under spined if I start increasing weight.

I’m starting to think I should have went with a 340 spine instead of 400. Then I could have gotten to a higher arrow weight without being under spined. Surprised the shop didn’t give me that option. Guess it’s my fault for a lack of knowledge at the time & not asking more questions.