Bethlehem Steel, 1940, producing big guns for the Navy, 16" battleship gun

they were shrink fit in laminated sections. The main barrel was made in 2 sections the outer barrel and the machined shell section, the outer section was hung in a giant pit heated and the inner section was lowered in then cooled. This the section where the shell and powder was placed wore out and with the shrink fit it could be reheated and replaced and refurbished easily.

The whole barrel was made in sections the area from the breech up to cover the shell and explosive did not have any rifling. Interesting photo as it shows all the different laminations.

https://industrialscenery.blogspot.com/2016/11/building-and-testing-naval-guns.html

In 1954, all of the Battleship New Jersey's massive 16" guns were replaced. 

The nine guns had been used during World War II and the Korean War. 

The guns were relined and test fired in 1969.

 Three of the barrels were in storage for decades at the St. Julien's Creek Annex U.S. Naval support facility in Portsmouth, Virginia.

 To save these historic barrels from being scrapped, the Battleship New Jersey and the Mahan Collection Foundation transported them for permanent display in Camden and Basking Ridge, New Jersey, and the Philadelphia Navy Yard. 

Each barrel is 68 feet long and weighs 120 tons. The barrels were transported north by Norfolk Southern. To support the barrels' restoration or for more information about this project, visit www.battleshipnewjersey.org/40