exit wound / bullet going through someone ---happy

I understand that after the 60's and no blood when people getting shot with guns, it was time to get a little more realistic in the 70's. They were so exit wound/blood happy with this film that there were mistakes made in order to make it look like a bullet went through someone's chest and a wound coming from their back exiting (or vice versa). When the one guy gets shot with a .45 caliber bullet in the front they show his back from camera view, he still is living but is needing aid and helped along but show no blood in the front from an entrance wound(in clear view) when being helped. Another gets shot in a restroom and slo-mo-ing the shooting, the mirror behind him gets shattered and there's blood spatter but looking at where he got shot in the chest and the big spot on the mirror which would have been where the bullet hit doesn't line up quite right.