Underspined arrows = dry firing ?

1164 Views 27 Replies 14 Participants Last post by Shogun1, 3 mo ago

HidingFromMyWife

Discussion Starter · 3 mo ago

Curious. If I have a 70# bow and shoot a 350gr arrow, it's not considered "bad" for the bow. And let's say that arrow is 300spine.

But what if that 350gr arrow is underspined (say, 500sp) and just loaded with inserts and a heavy field point. Could it potentially cause damage to the bow once fired ?

My theory is maybe. The arrow wouldn't be able to absorb all of the bow's energy? Does anyone know if there is any validity to this ?

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Shogun1

· #2 · 3 mo ago

“Could it potentially cause damage…?”

Yes.

Might you get lucky and the arrow absorb enough energy to preclude damage to the bow? Sure — you might.

Might you get lucky and the arrow hold together long enough to leave the bow? As opposed to flexing enough to break during the shot.

Sure you might. But you also stand a good chance of putting some of that weak arrow through your arm or hand.

The question is “Do you feel lucky today?”

Presumably, running the numbers to get as close to 5 gr per pound or draw weight is part of a quest for speed. But is that little bit of speed worth the risks you take?

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SonnyThomas

· #3 · 3 mo ago

HidingFromMyWife said:
Curious. If I have a 70# bow and shoot a 350gr arrow, it's not considered "bad" for the bow. And let's say that arrow is 300spine.

But what if that 350gr arrow is underspined (say, 500sp) and just loaded with inserts and a heavy field point. Could it potentially cause damage to the bow once fired ?

My theory is maybe. The arrow wouldn't be able to absorb all of the bow's energy? Does anyone know if there is any validity to this ?

You're still launching a 350 gr arrow. Doubtful that damage would occur. The only arrows I know of that couldn't take compound bow force were wood arrows. Take a .500" spine and flex it. It'll bend a "mile" before it breaks.

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VXR ripper

· #4 · 3 mo ago

SonnyThomas said:
You're still launching a 350 gr arrow. Doubtful that damage would occur. The only arrows I know of that couldn't take compound bow force were wood arrows. Take a .500" spine and flex it. It'll bend a "mile" before it breaks.

This is the correct answer. There wouldn’t be any effect similar to a dry fire unless the arrow was so weak that it broke before it left the string.

A lot of the “arrow absorbing energy” talk around here is either misconstrued or just flat out made up.

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VXR ripper

· #5 · 3 mo ago

Ask yourself this.

Would you shoot a 4gpp 200 spine arrow just because it’s stiff?

Reactions: 1

SHPoet

· #6 · 3 mo ago

HidingFromMyWife said:
Curious. If I have a 70# bow and shoot a 350gr arrow, it's not considered "bad" for the bow. And let's say that arrow is 300spine.

But what if that 350gr arrow is underspined (say, 500sp) and just loaded with inserts and a heavy field point. Could it potentially cause damage to the bow once fired ?

My theory is maybe. The arrow wouldn't be able to absorb all of the bow's energy? Does anyone know if there is any validity to this ?

Yes it could and it could damage YOU. It's all about the stiffness.

Reactions: 1

SonnyThomas

· #7 · 3 mo ago

Years back, back when Carbon Express introdued the CXL, 150, 250 and 350. The CXL 150 has a spine of .510". These were like glass, fragile to beat the band. Friend and I had to try the 150s. They shot great, but broke on 3D targets of times and these were the old harder McKenzies. They broke flush at the depth in the target. I was using a 62 pound bow with 29" draw. We soon switched to CXL 250s. Later on Carbon Express much improved the CXL 150 - I think the CXL 150 SS. Again, I shot them and they were great, accurate and didn't break at the target.
Later on I used a faster bow with the newer CXL 150 Pro and again accurate, but broke at flush deep in the target.

I have since stayed with .400" spine arrows.

Never once have I heard of a reasonable under spined arrow breaking at the shot - aluminum or carbon. I'm not saying some .600" or weaker spined arrow. Again, I've known of some trying wood arrows in compound bow and met with really bad results.

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SonnyThomas

· #8 · 3 mo ago (Edited)

Also years back we shot CX300s (.370" spine) with 70 pound bows. I used short CX200s (.458" spine) for at least two years with a 62 pound bow with 29" draw. Dang accurate and from a Hoyt overdraw riser.

TMan51

· #9 · 3 mo ago

HidingFromMyWife said:
But what if that 350gr arrow is underspined (say, 500sp) and just loaded with inserts and a heavy field point. Could it potentially cause damage to the bow once fired ?

My theory is maybe. The arrow wouldn't be able to absorb all of the bow's energy? Does anyone know if there is any validity to this ?

There are lots of gory pictures that say you are correct in your assumption.

jo3st3

· #10 · 3 mo ago

Bows are suppose to be able to safely shoot, at their minimum, a 5 grains per pound arrow... aka 350 grains at 70#. As we all know, that's how they determine IBO for the bows.

With that said, you're probably stressing the system to the max and eventually I would think it puts more wear and tear on the bow. Think of it like red lining an engine. Do you really want to red line the bow? Try to shoot for something like 5.5 gpp or even 6 if you're trying to shoot a lighter setup.

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SonnyThomas

· #11 · 3 mo ago

TMan51 said:
There are lots of gory pictures that say you are correct in your assumption.

You've been around here long enough to know better. Many of the pictures were repeats. Of the original post no one noted the arrow being under spined. The arrows damaged to start with, just never checked.

Only one I know of told he had put his broke arrow back in the quiver and then mistakenly pulled and shot it. The arrow went into index finger. Turned around and asked the club to help with hospital bill. Club's insuranced paid and drop the club. I personally know the shooter and the club.

SonnyThomas

· #12 · 3 mo ago

jo3st3 said:
Bows are suppose to be able to safely shoot, at their minimum, a 5 grains per pound arrow... aka 350 grains at 70#. As we all know, that's how they determine IBO for the bows.

With that said, you're probably stressing the system to the max and eventually I would think it puts more wear and tear on the bow. Think of it like red lining an engine. Do you really want to red line the bow? Try to shoot for something like 5.5 gpp or even 6 if you're trying to shoot a lighter setup.

Not full throttle But. My 2000 Hoyt UltraTec set 62 pounds with 29" draw shot a 326 gr it's entire life. Must have 40,000 through it. Last time shot was 2010. Just as fast and as accurate as ever. 326/62= 5.258 grs per pound.

Reactions: 1

Double_D_

· #13 · 3 mo ago

HidingFromMyWife said:
Curious. If I have a 70# bow and shoot a 350gr arrow, it's not considered "bad" for the bow. And let's say that arrow is 300spine.

But what if that 350gr arrow is underspined (say, 500sp) and just loaded with inserts and a heavy field point. Could it potentially cause damage to the bow once fired ?

My theory is maybe. The arrow wouldn't be able to absorb all of the bow's energy? Does anyone know if there is any validity to this ?

5gpp is 5gpp no matter the spine.
However even that isn't a very good measure of the amount of excess energy a bow can absorb without damage.
As we all know, 350gr @ 70lb/23" isn't producing the same amount of energy as 350gr @ 70lb/31".

Reactions: 1

bigbuckdn

· #14 · 3 mo ago

jo3st3 said:
Bows are suppose to be able to safely shoot, at their minimum, a 5 grains per pound arrow... aka 350 grains at 70#. As we all know, that's how they determine IBO for the bows.

With that said, you're probably stressing the system to the max and eventually I would think it puts more wear and tear on the bow. Think of it like red lining an engine. Do you really want to red line the bow? Try to shoot for something like 5.5 gpp or even 6 if you're trying to shoot a lighter setup.

So mid 90s I had a then PSE Brute Force it was very similar to my Mach 6. I shot it for 2 years
at 4GPI I shot it a lot all the local clubs pout on 3D shoots there were shoots every sat and sun and lots of weekends I would do 2 shoots it held great then 1 day boom limb pieces everywhere pieces and parts flying string or cable can’t remember wrapped right around my arm. Somehow nothing hit me so yea it slowly over time weekend to the boom

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TMan51

· #15 · 3 mo ago

HidingFromMyWife said:
If I have a 70# bow and shoot a 350gr arrow, it's not considered "bad" for the bow. And let's say that arrow is 300spine.

You can easily hit that speed with a Victory XV300, even with a 30" shaft, and a 100gr tip. It will work just fine. It's not like a dry fire.

That stated, you will be getting close to the recovery rate of the limb with a dry fire. If you start with a heavier weight shaft(s), and check speeds as you drop weight, you can easily see that effect.
The other thing that's happening is the extra energy you didn't use pushing the heavier shaft, doesn't just go away. The rigging and limbs eat most of that, the rest is noise, and a very small amount of heat.

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jo3st3

· #16 · 3 mo ago

TMan51 said:
You can easily hit that speed with a Victory XV300, even with a 30" shaft, and a 100gr tip. It will work just fine. It's not like a dry fire.

That stated, you will be getting close to the recovery rate of the limb with a dry fire. If you start with a heavier weight shaft(s), and check speeds as you drop weight, you can easily see that effect.
The other thing that's happening is the extra energy you didn't use pushing the heavier shaft, doesn't just go away. The rigging and limbs eat most of that, the rest is noise, and a very small amount of heat.

and that energy goes into the shooter too in the way of vibration through the grip.

TMan51

· #17 · 3 mo ago

jo3st3 said:
and that energy goes into the shooter too in the way of vibration through the grip.

Oh yeah. Think of yourself as a big Limbsaver.
Current designs are much better with that. My Supertec's from the early Y2K era were enough that it bothered my hands on a 28 target field round.

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SonnyThomas

· #18 · 3 mo ago

jo3st3 said:
and that energy goes into the shooter too in the way of vibration through the grip.

I got to shoot the Bowtech Black Knight when it first came out. Dealer had it set up and had me shoot it. Lord! It hit 350 fps alright and kicked like a young mule.

Reactions: 2

retrieverfishin

· #19 · 3 mo ago

Ironically we just shot our 87lb gt500 today to test out potential backstop. One of the arrows was a 500 spine fmj. Did just fine and would be fine for the bow to do 100's of times.

Reactions: 1

Shogun1

· #20 · 3 mo ago (Edited)

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