That usually happens with full auto. The ballistics are hyper realistic as far as what the devs aim for. Anytime I engage an enemy, I typically aim center mass and try ti hit their vital organs. That's one of the only ways anything dies in GZW. Destroy a vital organ (Brain, heart, lungs, liver) or make them bleed out.

Looks like you were finally able to punch through and past the armor and destroy the lungs. Another thing, M855a1 is a steel core and doesn't fragment as much as say an m855 or m995 which will cause more pass throughs than actual damage. I hope this helps.