Originally Posted by
Roundballer
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".