Where was the Predator's Cannon Gun located?
Didn't see any on his shoulder this time!
Or was he shooting from his helmet?
And how the hell did his mask target his own head at the end?
From what I understand from a couple of articles I've seen, this is meant to be leaner, less heavily armed Predator. He does not have a shoulder cannon. He does have the long "flechette" device targeted by his helmet, the cloaking technology, the floating mines, and probably a few other things.
He head was targeted because Naru figured out that the flechettes would be directed to wherever the targeting beams were set. She had stolen the helmet earlier in the fight and set it by the bog. When he rose up after initially sinking, he fires a flechette and she activates the helmet, aiming the beam at his head; and viola! the flechette kills him.
Now, are there issues with all that? Absolutely. While I can accept that any intelligent person in that situation can deduce that the flechettes fly to wherever the little red dots appear, I don't see how she could figure out how to activate or aim it. Even someone from a high-tech society would be unlikely to figure out in that short amount of time how to do it.
In addition, we have the issue of how she knew where to aim the beams. She had it wedged in a rock. Where the Predator might rise from the bog (and how she knew that would happen) is not predictable. I suppose she was just ready to use it whenever he crossed into the right place; but, again, it would only work if the predator fires the flechettes and how would she know he would fire it at that point is unexplainable.
Author of the Sodality Universe
The Road from Antioch
In the Markets of Tyre
Flight to Lystra
The Theater at Ephesus (coming soon)
The Council on Jerusalem (coming 2023)