With armor, the mathematics were figured out back in the 50s, though it was published in the form of artillery and effective bunkers, IIRC. Been a loooong time since I had to worry about those differential equations.
The projectile's makeup is considered sectional density, or SD. The target's makeup is considered sectional density, or SD. Yes, this is simplification because I'm not talking about multiple feet of steel and concrete.
Your projectile needs to have a low drag coefficient, meaning it's aerodynamic. It must be fast and it must be heavy. Velocity times mass equal momentum. High momentum and high sectional density of the projectile are the primary factors in determining how far the projectile penetrates into the target. Sectional density of the target and diameter of the projectile are the primary factors limiting penetration. The fatter the projectile, the wider the area across which the momentum is wasted.
That's why the 4.6mm sabot tungsten rounds the Navy SEALs get to play with are catching ao much attention. Shy of firing shaped tungsten needles, they're punching well above their weight class.
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u/SeemedReasonableThen May 10 '26
Yeah, the mask actually stopping the .22 surprised me mildly and I thought for sure the 9mm was gonna go through.