If you ever get the opportunity get some nice round watermelons and stand 60 yards away and shoot them with a .30 cal rifle.
You will be amazed that the watermelon stuff can splash through any direction.
Hydraulics in action.
Which way the 'stuff' appeared to fly means nothing about where the shot came from.
Here is an autopsy photo where you can see the entrance wound in the back of JFKs skull. Hydraulic pressure blew out the right side of his skull which you can also see in the image...
Sorry to be so graphic, but after 50 years of hearing this stupid conspiracy shit, maybe it's time to be 'graphic'.