USN WWII 5 in-38
This 5 inch gun would be a smaller caliber rail mounted artillery piece. Here it is in WWII on board USS Laffey (DD741) under attack by Kamikazes and an add'l link to a full explanation of the gun, its mount, ammunition, (storage and handling) and operation in action.
The narration is incorrect in stating the rate of fire was 22 rounds per barrel per minute. It was 12 to 18 RPM.
(The 120mm AAA gun (4.7 inch) that I served on was capable of 11 rounds per minute.)
for a very complete explanation of the weapon and it's installation, see