Note the brass falling to the deck below the smoke. Does that get ejected out of the red port above the barrel?
Newer destroyers (DDG 81 and up) use the newer Mod 4 5″/62 caliber Mk 45 gun. In naval cannon, “calibers” refer to the length of the barrel compared to its diameter. A 54 caliber gun (pictured here) has a length of 270 inches (5″ x 54 calibers). The Mod 4 62 caliber gun has a barrel length of 310 inches which provides an extra 150 feet per second of muzzle velocity.
I don’t know if there are plans to upgrade existing ships to the Mod 4 or even if it’s really worth the cost.