Continuity mistake: When the helicopter lands we see it is sitting over the white circle of the landing zone on the back of the ship. Later, right after the F18 is shot down, we see an aerial view of the ship with a small part of the back cut off, but part of the landing zone circle is visible and there is no helicopter. (00:13:30 - 00:36:00)
Continuity mistake: Before Admiral Bates first speaks to Strannix, there is a dark-haired marine in a green uniform on his left. When Bates raises his hand to signal activating the audio to speak, Captain Garza (black uniform and silver hair) is suddenly on his left. Then it changes to another camera angle and the marine is back next to Bates. (00:36:40)
Answer: The smaller guns were only equipped with the Starburst rounds. The 16 Inch Cannons were still supplied with live ammo. None of the characters left to fight had experience with the 16 inch guns except for the Gunner's Mate, therefore none of them thought to use one of the 16 inch guns.
dablues7