Other mistake: Near the end of the film, when the 2 nuclear missiles are destroyed, one by a fighter plane, the other by Segal, the same shot is used for both the missiles blowing up.
Other mistake: In each film Segal plays a chief petty officer, who happens to be an ex-Navy SEAL. In the posters for Under Siege, he's shown in the dress white uniform of an admiral. In the second film he's still depicted as an officer, but he has been demoted to a lieutenant. I guess the producers just thought the officer's uniform looks prettier, even though they're the very same uniform, except a chief has anchors on his collar and no shoulder boards.
Other mistake: When Seal Team 5 was sent to the Missouri, according to the admiral, they were aboard a CH53E. The helicopter they were shot down in was a CH46.
Other mistake: When the band is playing in the mess-hall you hear the drums playing along. When Ryback enters the mess-after after the take over, no drums are on stage.
Other mistake: When Commander Krill gains access to the captain's safe to retrieve the disc, the safe has no locks. (00:24:20)
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