with a frontal torso shot most any service caliber round can over penetrate easily.
ballistic gelotin is homogenous, humans are not.
a lung shot below the nipple area will encounter little muscle or fat, may stike a rib or pass between ribs, got through a lung which is quite hollow in terms of dense tissue and go out the back again maybe striking a rib or passing between them and strike little muscle. this is just anatomy.
if the round hits the pectoral muscle it will encounter dense muscle, maybe a rib, and possibly the scapula.
except for the sternum, heart, or pectorals, there isnt much desity in the upper part of the torso. while the abdomin will have more desity as will the limbs.
as stated before by others, more shots miss there intended target than hit it during a real life gun fight or other type of criminal attack.
shot placement is the deciding factor, bullet design is a far second place.
with Sarah Jane, Leela, Romana, Nyssa, and Tegan.
Facts are no match against enthusiasm and ignorance...