# Damage Assessment



## drgreen (Feb 21, 2011)

The shots were taken with 3/8 steel with tex field bands at 20m. One actually managed to penetrate the steel water bottle. The bottles were standing on a table, not hung up with string.

With larger steel like 12mm, it seems like the projectile knocks the bottle off the table before it can penetrate it as much. So, I was wondering, what is the key to having deeper penetration with a SS:

Is fps more important?

Or the energy behind a heavier, but slower projectile?

















Can someone please tell me how you post pictures without linking also? Thanks.

EDIT: Thanks, I needed to enable the multiple picture uploading feature which I have done now.


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## Rayshot (Feb 1, 2010)

drgreen said:


> The shots were taken with 3/8 steel with tex field bands at 20m. One actually managed to penetrate the steel water bottle. The bottles were standing on a table, not hung up with string.
> 
> With larger steel like 12mm, it seems like the projectile knocks the bottle off the table before it can penetrate it as much. So, I was wondering, what is the key to having deeper penetration with a SS:
> 
> ...


Great pics, first of all.

To put your pics directly on the post. When you are creating the new post (subject), look for the button that says "Click To Attach Files". It is a dark blue button. Then it will automatically (at least with my computer) bring up places to get files from on your computer. I go to "Photos" as I have a Mac. Then I have to choose (highlight) the photo, then click the button on the bottom that says choose. then it should start loading to your post as a file to insert into your post where ever the cursor was last positioned.

Hope that is clear enough.


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## mainaman (Apr 16, 2011)

drgreen said:


> The shots were taken with 3/8 steel with tex field bands at 20m. One actually managed to penetrate the steel water bottle. The bottles were standing on a table, not hung up with string.
> 
> With larger steel like 12mm, it seems like the projectile knocks the bottle off the table before it can penetrate it as much. So, I was wondering, what is the key to having deeper penetration with a SS:
> 
> ...


Energy depends on mass and velocity, so you have to account both for the mass and fps. I would htink also the band type will matter, but in the end I think(hope I am not wrong) ligher ammo will do the job better than heavier ammo.


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## Henry the Hermit (Jun 2, 2010)

If all you want to do is punch holes in cans, small ammo/high speed will do the job. If you want to kill game, you need high energy which is completely expended on the game. A projectile which zips right through a rabbit may not kill it. So, small and fast = penetration, big and fast = deadly. Try filling some cans with water and shoot them with 3/8 steel, then .50 cal lead, both at 160 fps.


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## kobe23 (Jun 28, 2010)

Some simple physics.
Pressure is force/area, therefore when the same amount of force is applied, small area result in high pressure and otherwise.
Make things simple, just like a nail and a steel hammer. When you hammer a wood, it barely dent, but when you nail the wood, penetration happen like nobody's business.

When 2 projectile, 1 bigger heavier and another smaller lighter, are travelling at the same speed, the bigger projectile produce bigger momentum therefore deeper penetration.
However when both projectile are given same force, the smaller projectile will accelerate much faster compared to it's counterpart and with consideration of the small surface of area of contact, would result higher penetration.

Well sometimes the type of material of the target does make a difference..


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## drgreen (Feb 21, 2011)

kobe23 said:


> Some simple physics.
> Pressure is force/area, therefore when the same amount of force is applied, small area result in high pressure and otherwise.
> Make things simple, just like a nail and a steel hammer. When you hammer a wood, it barely dent, but when you nail the wood, penetration happen like nobody's business.
> 
> ...


Yea I thought so, I was looking for some confirmation on this matter. Since cans are more brittle than flesh and skin, the smaller but faster projectile is likely to penetrate it deeper.

But I am also wondering if its to do with the fact that the bottles were not hung up, and therefore the .50 knocked it over before doing much damage. I tried hanging the bottles and the damage does seem to be more significant, ripping holes into the fairly thick steel.

Pictured: Headshot if it was a bunny poking its head out!


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## kobe23 (Jun 28, 2010)

I believe if the bottle is hung, more energy will be forced into the bottle more efficiently. If the bottle is standing on a surface without any support, when hit at the bottom or the top, it would rotate. However if hung, there would not be much free rotation as the string is already in tension before the bottle start to rotate.


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## Henry the Hermit (Jun 2, 2010)

Aluminum cans are fun to shoot, but a terrible indicator of performance or penetration.. I can shred an aluminum can just about as fast with my derringer (below) and .25 cal steel as I can with a 12+ lb/ft .50 cal ball. Below are some examples.

First, the derringer 3/4 inch 2to1 taper Theraband flats (Thanks, Dan aka ZDP-189), sends a .25 cal steel ball at 250 fps.










Here's the result of one hit with the derringer at 7 yards. It went all the way through.










Next is a hole in one of my coconut palms made by a .50 cal lead ball traveling at 165 fps. The ball is resting in the hole a bit more than an inch deep.










And here is a .375 lead ball at about 165 fps in the same tree.


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## drgreen (Feb 21, 2011)

Nice pics, thanks for sharing.

Yea I agree cans are an inadequate way of testing power and penetration since they're too thin, almost anything will go through. Thats why I used the steel water bottles, you need a certain speed with 3/8 steel to pierce it, otherwise it will only dent. And it ensures that I hit the centre of the bottle, since a side hit will be deflected and only cause a minor dent.

Im going to test .50 on a hanging bottle soon to see if I can achieve the same, but it looks promising so far from your comparison on the tree bark.


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## NaturalFork (Jan 21, 2010)

if you want penetration, higher FPS and smaller ammo.


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## Melchior (Dec 27, 2009)

It's a bit of a tricky question. The heavier your projectile, the more does it get of the overall share of energy that is spent by acceleration of ammo, pouch, bands and the hysteresis (inner friction) of the bands. Your slinghsot setup (weigh of pouch, type of bands, weight of bands, draw length etc) dictate how much you profit form heavier ammunition. 
On the other hand, a small, fast projectile will penetrate deeper...and different targets react differently on fast vs. slow, powerful shots....

so, the answer depends on your slingshot setup and your target. For example, an "albatros/butterfly"-style slingshot with a very small pouch gets crazy speeds with small ammo. A slingshot with heavy tubes and a big pouch will do better with a .45 lead ball. Some chinese songbird hunters I got in contact with (no, I don't encourage what they do) state that small 6-8mm steel balls are best for the small birds because of their "explosive" effect, and they prefer it much to larger ammo, while they use 12mm steel for rabbits and such.


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## drgreen (Feb 21, 2011)

Melchior said:


> It's a bit of a tricky question. The heavier your projectile, the more does it get of the overall share of energy that is spent by acceleration of ammo, pouch, bands and the hysteresis (inner friction) of the bands. Your slinghsot setup (weigh of pouch, type of bands, weight of bands, draw length etc) dictate how much you profit form heavier ammunition.
> On the other hand, a small, fast projectile will penetrate deeper...and different targets react differently on fast vs. slow, powerful shots....
> 
> so, the answer depends on your slingshot setup and your target. For example, an "albatros/butterfly"-style slingshot with a very small pouch gets crazy speeds with small ammo. A slingshot with heavy tubes and a big pouch will do better with a .45 lead ball. Some chinese songbird hunters I got in contact with (no, I don't encourage what they do) state that small 6-8mm steel balls are best for the small birds because of their "explosive" effect, and they prefer it much to larger ammo, while they use 12mm steel for rabbits and such.


I didn't consider the weight of the pouch and bands as significant, but the smaller your ammo size, the more wasted energy as a proportion of total energy spent. So I guess that is proof of matching ammo size to band power and weight in order to be efficient.

That is just a criteria for efficiency though, not necessarily the fps or joules. It will indirectly affect it though. So given my band setup, if I can test that 3/8 is inefficient, then the .50 will be more efficient relatively. I think this means that I can lighten the band and still have the same performance denoted by fps and joules with the 3/8 caliber.

This is off topic now, i was just considering what you said. I think the intuition still holds: lighter, smaller, faster = more penetration, heavier, bigger, slower = less, given the same draw force.

Thanks for the insight.


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## BullsEyeBen (Apr 21, 2011)

Had a similar post in general forum regarding corrigated iron and computer monitors hav a look- but yea I agree small balls dont have the momentum but travel faster. Big balls have a larger surface area there for has more material to punch through at slower speeds. A compromise of these factors should help, as others hav put in detail- good work.B-)


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