Mark 9 4-in./50-cal. Gun

The 4-inch/50-calibre gun is an American 102mm naval gun used in a variety of small warships such as submarines and destroyers, as well as a wide variety of utility ships such as the Liberty-class Cargo Ship. It is breech-loading and has a maximum range of 14.5km at maximum firing angle. While not particularly impressive in any metric, its design (the most modern and widely produced Mark 9 variant being from 1914) was effectively used to arm ships that weren't really meant to fire their guns except in grave circumstances or with the upper hand. Thanks to its enormous production numbers, the American 4-inch gun is one of the most common types of naval artillery in Oceanykan gunboats, coastal raiders and fleet escorts.