Yesterday on customs, my buddy and myself was over by USEC building and a scav was walking down the wall on the inside. My buddy shot him 5 times in the head and it finally died on the 5th shot. I saw 5 bullet holes in the wall where he shot the scav every time but only the last shot had blood splatter on the wall. He went live on discord and shared his screen with me and he showed 5 bullet holes in the wall with 5 blood splatters. He also said the scav started yelling and took off running, the scav on my screen never made a sound and slowly just walked down the wall, never ran.
So that lets me know that 4 of his shots didn't register on the SCAV as I only saw 1 blood splatter on the wall but 5 holes, he saw 5 holes and 5 blood splatters, but only the last shot counted it seems, also the scav never ran or made a sound on my side, but on his side it ran and started yelling at him.
I just keep seeing posts about people saying they are shooting scavs in the head but they are just tanking the shots like nothing happened, thats most likely because the shots didn't actually register.