[HeadOn]

Check your units (use kg, not g), and don’t forget to square the velocities...

Rock - 72.3 joules
Bullet - 894.3 joules

[Hodar]

ouch ... that left a mark.

[VeniVidiVici]

Rock - 72.3 joules Bullet - 894.3 joules

That's right. Blame it on the joules.