All of this tells me that the old idea of using a Gauss rifle to deliver Elementals to a battlefield is a very bad idea.
Not if they hit the target.
I do wonder how many physics-defying conceits are needed to make a setting like Battletech work.
Using just iron (7.874 g/cm³), a perfectly spherical shell (and a diameter of 0.3), and a conservative 6,000 m/sec speed, impact angle of 15 degrees, hitting rock in standard gravity:
Results:
Yield Scaling 0.53 x 101 meters
Pi Scaling (Preferred method!) 1.41 x 101 meters
Gault Scaling 6.88 meters
Crater Formation Time 0.63 seconds
Using the Pi-scaled transient crater, the final crater is a Simple crater with a rim-to-rim diameter of 2.19 x 101 meters.
This impactor would strike the target with an energy of 2.04 x 109 Joules (4.86 x 10-7 MegaTons).
If we ramp it up to nickel (8.9 g/cm³), an oblate with 2/3 the diameter (0.2), and a 30,000 m/sec speed, impact angle of 30 degrees, hitting rock in standard gravity:
Results:
Yield Scaling 1.13 x 101 meters
Pi Scaling (Preferred method!) 2.69 x 101 meters
Gault Scaling 1.61 x 101 meters
Crater Formation Time 0.767 seconds
Using the Pi-scaled transient crater, the final crater is a Simple crater with a rim-to-rim diameter of 4.19 x 101 meters.
This impactor would strike the target with an energy of 1.68 x 1010 Joules (4.01 x 10-6 MegaTons).
Both of those yield craters in the hundreds of meters wide, which is impressive.