I have hit two deer squarein the shoulder. the first was a doe that I hit with my 170 fps bow and 85 grain broadhead. the muzzy went right through the shoulder, through the heart and the head made it out the other side. deer went 30 yards down hill. But then you couldn't get a shot more centered in the heart.

My second was a buck last year. he ran like the dickens for 100/150 yards before we found him. hardly any blood.

are you using huge cutting diameter expandables? I don't use expandables because I'm scared of what would happen if i hit the shoulder directly.