Used in many USN battleship and cruiser classes in 1920s to 1940s:

Nevada (BB-36), Pennsylvania (BB-38), New Mexico (BB-40), Tennessee (BB-43), Colorado (BB-45), Pensacola (CA-24), Northampton (CA-26), New Orleans (CA-32), Portland (CA-33) and Brooklyn (CL-40) classes

Used also in USN submarines in the 1940s

The set includes turned brass barrels. It is very simple to use in Your model, and makes it extremely realistic. Simply cut off the original plastic barrel and drill a hole in the remaining part and insert the metal barrel using Cyanoacrylate adhesives.