Shooting at lead targets... for science!

[Scandiacus]

Disclaimer: I have zero background in shooting at steel or other metal targets, so my question may be stupid.

My brother is studying impact cratering geology for his PhD in planetary science and has requested my help (and my guns) for an experiment. He routinely experimentally studies impacts in the lab using sand targets and a giant Catapult of Science, but there's also value in studying impacts in a soft, non-granular solid (ie, not sand), which is hard to do in the lab with the velocities his catapult is capable of. So he's suggesting using a rifle to shoot into a wax target. My concern is that even a .22lr is likely to totally penetrate a wax target of manageable size and, even if it doesn't, the massive difference in density between projectile and target will lead to poor experimental results. I'd like to suggest shooting at a lead target (1/2 to 1 pound lead ingots) so that the densities are more similar, and have come up with the following safety considerations/questions:

- Each lead target may only be shot once per side to avoid ricochets due to surface deformation.
- Lead targets should be angled slightly toward to the ground (20 degrees?)
- Shots should be from at least 50 yards

We'll most likely be shooting .22lr and possibly very light .223 loadings.

Are there other safety considerations I've not thought of? Is this whole thing a terribly bad idea?

[luckless]

Consider modelling clay as a medium? Also, an air gun with round balls might be a better simulation. The speed can be changed while the mass remains constant. I think bullets designed to penetrate may, by definition, skew the results.

[DrScaryGuy]

maybe a light loaded 410 shotgun? you could customize the load a lot easier that way too, whether you wanted to use different materials to simulate meteorites of different composition.
You could probably even use a chronometer to get load velocity data, then use a raised platform to shoot down at whatever your desired material might be.

fyi, somebody at wayne state is using pig bodies and C4 to simulate blast injury, so don't feel like you're way off the mark in terms of crazy science

[AxlMyk]

How about a muzzle loader shooting a ball. Wouldn't that be more like a lab test?

[Scandiacus]

Actually, modelling clay sounds like a really good idea. I like the idea of using an air gun, .410, or especially a muzzle loader, but unfortunately don't have any of those - lightest shotgun load I could do would be out of a 20 gauge. Hmmmm, maybe I should see this as an opportunity to buy another gun.... :naughty:

[dice]

I've got two .410s if you want to use one. I think the tests would be cool to watch.


Dice

[luckless]

Actually, modelling clay sounds like a really good idea. I like the idea of using an air gun, .410, or especially a muzzle loader, but unfortunately don't have any of those - lightest shotgun load I could do would be out of a 20 gauge. Hmmmm, maybe I should see this as an opportunity to buy another gun.... :naughty:

Basic, used muzzleloaders can be really inexpensive.

[AxlMyk]

Another thought, go to Walmart and get a Daisy Red Ryder for $25. I just bought one a week ago.
You can have fun with it after the testing.

[Roundballer]

Disclaimer: I have zero background in shooting at steel or other metal targets, so my question may be stupid.

My brother is studying impact cratering geology for his PhD in planetary science and has requested my help (and my guns) for an experiment. He routinely experimentally studies impacts in the lab using sand targets and a giant Catapult of Science, but there's also value in studying impacts in a soft, non-granular solid (ie, not sand), which is hard to do in the lab with the velocities his catapult is capable of. So he's suggesting using a rifle to shoot into a wax target. My concern is that even a .22lr is likely to totally penetrate a wax target of manageable size and, even if it doesn't, the massive difference in density between projectile and target will lead to poor experimental results. I'd like to suggest shooting at a lead target (1/2 to 1 pound lead ingots) so that the densities are more similar, and have come up with the following safety considerations/questions:

- Each lead target may only be shot once per side to avoid ricochets due to surface deformation.
- Lead targets should be angled slightly toward to the ground (20 degrees?)
- Shots should be from at least 50 yards

We'll most likely be shooting .22lr and possibly very light .223 loadings.

Are there other safety considerations I've not thought of? Is this whole thing a terribly bad idea?

I have been thinking about this since you posted, yesterday. And, this is going to be long.

First, what are we trying to simulate in this experiment?
As I read it from your post, the answer is meteor impact on a planet/moon.

I would suggest, for this exercise, to discuss this as if it is the moon, and use that to eliminate or reduce the influences of things we can't simulate, ie. the earth's or other planets atmosphere.

Now, the "target". The moon's mass is (google) 16.2 x 1022 lbs. And there are 7000 grains/lb.

In order to get things even close, mass of meteor (bullet) vs mass of target (moon), you would have to assume that the target needs to be the "immovable" object. So, it needs to be ridged affixed to its stand.

The shape and composition of the target needs to somehow resemble surface and composition of a planet/moon. Since we are talking about lead as the material of the "meteor" (bullet), the "bed rock" of the target should also be lead. The surface of the target needs to be convex, so that it also resembles a planet/moon. The more convex the surface is, the smaller the planet/moon it would represent. I would suggest a radius of a couple of feet for the surface, but you only need about 6" for a target diameter, and it should be THICK to limit flex on impact.

The very outer surface of a planet/moon would not be the same as the substrate/bedrock. I would go with the modeling clay suggested above. Get the type that is air or oven dry to simulate the softer dirt layer. I would also keep the thickness down to 1/4 inch or less. And you can have different "hardness" with different amounts of "cure" on the clay.

Now, the "meteor" needs to be limited to the same materials as the planet/moon substrate, so lead only! No jacketed ammo, that would induce other variables and skew the results. Beside the fact when you start getting into those velocities, you will rip right through the target, and the mass would represent a HUGE meteor of global annihilation proportions. Keep it to 22lr, and try different weights in the 32, 36, 40 grain area, and differing velocities of commercial ammo in the 700~900, 1030~1070 and 1250~1300+ ranges of "subs", "standard" and "high velocity" stuff.

Finally, actually shooting this:
Your suggested range of 50 yrds is at least twice what you need. I have shot fixed A36 steel at 25 yrds with a .22lr with NO splatter coming back (sideways, up and down, yes, but nothing makes it back towards the shooter). Don't worry about angling the target, the bullet will break up on the substrate and follow the surface of the substrate. And if you make the targets larger, and you are good enough of a shot, you can get a couple of "specimens" from each target. Just try to not hit previous hits, that will destroy what you are trying to simulate with a "meteor crater".

[Scandiacus]

I have been thinking about this since you posted, yesterday. And, this is going to be long.

First, what are we trying to simulate in this experiment?
As I read it from your post, the answer is meteor impact on a planet/moon.

I would suggest, for this exercise, to discuss this as if it is the moon, and use that to eliminate or reduce the influences of things we can't simulate, ie. the earth's or other planets atmosphere.

Now, the "target". The moon's mass is (google) 16.2 x 1022 lbs. And there are 7000 grains/lb.

In order to get things even close, mass of meteor (bullet) vs mass of target (moon), you would have to assume that the target needs to be the "immovable" object. So, it needs to be ridged affixed to its stand.

The shape and composition of the target needs to somehow resemble surface and composition of a planet/moon. Since we are talking about lead as the material of the "meteor" (bullet), the "bed rock" of the target should also be lead. The surface of the target needs to be convex, so that it also resembles a planet/moon. The more convex the surface is, the smaller the planet/moon it would represent. I would suggest a radius of a couple of feet for the surface, but you only need about 6" for a target diameter, and it should be THICK to limit flex on impact.

The very outer surface of a planet/moon would not be the same as the substrate/bedrock. I would go with the modeling clay suggested above. Get the type that is air or oven dry to simulate the softer dirt layer. I would also keep the thickness down to 1/4 inch or less. And you can have different "hardness" with different amounts of "cure" on the clay.

Now, the "meteor" needs to be limited to the same materials as the planet/moon substrate, so lead only! No jacketed ammo, that would induce other variables and skew the results. Beside the fact when you start getting into those velocities, you will rip right through the target, and the mass would represent a HUGE meteor of global annihilation proportions. Keep it to 22lr, and try different weights in the 32, 36, 40 grain area, and differing velocities of commercial ammo in the 700~900, 1030~1070 and 1250~1300+ ranges of "subs", "standard" and "high velocity" stuff.

Finally, actually shooting this:
Your suggested range of 50 yrds is at least twice what you need. I have shot fixed A36 steel at 25 yrds with a .22lr with NO splatter coming back (sideways, up and down, yes, but nothing makes it back towards the shooter). Don't worry about angling the target, the bullet will break up on the substrate and follow the surface of the substrate. And if you make the targets larger, and you are good enough of a shot, you can get a couple of "specimens" from each target. Just try to not hit previous hits, that will destroy what you are trying to simulate with a "meteor crater".

(Further disclaimer: I'm also not a planetary geologist - that's my brother's job)

My understanding is that the main objective is to try and detect the formation and collapse of a transient crater in a non-granular substance. Transient craters form during impact events and then collapse into the final crater within milliseconds. Experiments to study transient craters usually impact into sand; experiments using non-granular targets are rare. So the intent is to try and observe the transient crater morphology in a non-granular target using a high speed camera. Closely replicating impact events on known planetary bodies is less of a concern - it's more about developing the geologist's intuition for how these impacts occur, and any interesting or unexpected results can be further explored in a laboratory setting under more controlled conditions at a later time, and with a bigger budget.

The apparatus we've tentatively settled on is clay or very thick, goopy cement mix in a horizontal wooden frame on the ground - basically immovable for our purposes. We'll fire into it at a 45 degree angle (the selected angle for his and other studies into impact events), with a suitable backstop close behind to catch potential ricochets off the surface. For best results we want to get as close as we can to the speed of sound in the object - obviously most cartridges won't even approach the speed of sound in most solids or semi-solids, but according to him anything between 500 and 1000 m/s is still "close enough" for his purposes. We've selected a 45 grain .223Rem JHP as our meteor due to its high velocity and likelihood to fragment (meteorites tend not to stay intact), which according to a ballistics calculator should reach somewhere around 980m/s out of my 16.1" barrel. Anyone see a safety concern there?

Great suggestions, Roundballer, and I would've agreed with you about having the bullet and target be of similar composition. However, it turns out most meteor impacts occur at hypervelocities in excess of 3000 m/s which we just can't do with our equipment. At that extreme velocity, solid planetary surfaces tend to behave more like a fluid than a solid when they're impacted. So a ~1000m/s .223 hitting wet clay is a reasonable - if not ideal - approximation for this test. A convex target surface isn't necessary because planetary radii dwarf most meteoroids - to an asteroid smaller than a mountain (most of them), a planet's surface may as well be flat. And atmosphere is unfortunately just going to be part of our Grand Canyon-sized experimental error - unless someone has a vacuum chamber we can borrow, that is. :razz:

We'll be doing these tests in mid-November when he comes up to Michigan. I'll be sure to share any cool footage we get of the impacts. Thanks to everyone for the input, and keep it coming if you have more suggestions! :)

[nmuskier]

Speed of sound is only around 340m/s, or 1,150 fps. Pretty much any .22lr will do that. The media you are looking at might have a great variation in malleability depending on temperature. Something to consider in November.

As far as providing a convex surface, look at our Earth's surface. We are talking a big scale. Surfaces are effectively flat to meteor impact. Local topography has a far greater effect than the curvature of a spherical surface.

[DV8r]

There are examples of this in slow motion with lead ingot targets on YouTube, check some out to get a better feel for what may work best for his testing.

[Michaelk]

I guess you may need to get a chrono also, for sicence of course. And some high speed cameras capable of capturing the impact.

Wax projectiles in a sabot out of a 410 could also work.

Also if the fps using a 410 is too high then maybe an air cannon using a sabot. Just be sure to use all metal construction of the air cannon NOT PVC.

[Scandiacus]

Speed of sound is only around 340m/s, or 1,150 fps. Pretty much any .22lr will do that.

The speed of sound actually varies depending on the density of the medium, among other factors. Sound travels faster in liquids than in air, and even faster through solids. For example, the speed of sound in water is 1,484 m/s, and it's 5,120 m/s in solid iron. We want to get as close as we can to the speed of sound in the solid target medium.

[Scandiacus]

There are examples of this in slow motion with lead ingot targets on YouTube, check some out to get a better feel for what may work best for his testing.

Ooh, I'd like to see that. Do you have a link? I couldn't find any after a few minutes of searching YouTube.

[Scandiacus]

I guess you may need to get a chrono also, for sicence of course. And some high speed cameras capable of capturing the impact.

He's not too worried about precise velocity - this is more proof of concept, I guess, to see if we even can capture formation and collapse of transient craters. Calculating the likely velocity is sufficient for our purposes. We do have high speed video recording capability.

[Roundballer]

Ooh, I'd like to see that. Do you have a link? I couldn't find any after a few minutes of searching YouTube.

This is one of the better videos. It shows all kinds of impacts, but it doesn't tell you any specs on anything:

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This is a short one of shooting lead pellets at a small bar of lead. It is not as dramatic has the high power rifle impacts.

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[10x25mm]

Lead targets are going to create a fair amount of aerosol lead with these impacts on lead plates and the environmental Nazis are going to give you a hard time. Soft AA 1100 aluminum alloys are usually used for such studies.

You can achieve the same effect with other materials by selecting alternate projectile/target materials with comparable kinematic (not dynamic) viscosity ratios. There are a fair number of classified military studies of this subject, and a few unclassified studies sponsored by NASA. Google 'projectile impact study' using their scholastic search function.