16-inch/50-caliber Mark 7 gunbarrel life. It had a Welin breech block that opened downwards and was hydraulically operated. The screw box liner and breech plug was segmented with
20 cm/50 3rd Year Type naval gunguns were breech loaded with two cloth bags of smokeless powder. Third year type refers to the Welin breech block on this gun. Breech block design began
15.5 cm/60 3rd Year Type naval gunConstruction was of the monobloc type with autofretting and used a Welin breech block mechanism which could be operated either hydraulically or by hand
12 cm/45 3rd Year Type naval gun"Third Year Type" refers to the Welin breech block used and this should not be confused with the later Type 3 12 cm AA Gun developed by the Imperial