Tanks. Being tanks. - (Im reposting this because I found a better photo) The M829 is an American Armor-Piercing Fin-Stabilized Discarding Sabot tank round designed specifically for the M256 120mm L/44 smoothbore
Armor-piercing bullet - Wikipedia
Historical] Armour-piercing rounds - News - War Thunder
How do various types of armor-piercing rounds (kinetic, HEAT, HESH) disable tanks and kill their crew? - Quora
The Sabot Round Pierces Tanks and Liquifies Its Targets | War History Online