Non-Newtonian fluids are fluids that doesn't have the typical viscosity property of a fluid we know in general sense. When it has force, pressure, or heat applied it, it hardens up. as viscosity doesn't follow the Newton's law of viscosity.
But even if the non-Newtonian fluid hardens up, energy from .50 BMG probably is enough to overcome changes in the fluid.
From: Iraqveteran8888
