TIL that undefeated heavyweight champion Rocky Marciano’s punch was tested by Boxing Illustrated in 1963, and found to have more explosive energy than an armour piercing bullet.
Not that surprising when you think about it. Bullets operate on the principle of focusing force into an extremely small area, and armor piecing bullets just take that a step further by not deforming the moment they impact without adding any extra force. A heavy punch with the weight of an entire heavyweight behind it has so much more force than the few grams of mass a bullet has.