BL Mk VII returned to loading charges in silk bags after it was determined that with new single-action breech mechanisms a six-inch BL gun could be loaded, a vent tube inserted and fired as quickly as a QF six-inch gun.

Cordite charges in silk bags stored for a BL gun were also considered to represent a considerable saving in weight and magazine space compared to the bulky brass QF cartridge cases.

In World War II the gun was used to arm British troop ships and armed merchant cruisers, including HMS Rawalpindi, which briefly fought the German 11 in (280 mm)-gunned battleships Scharnhorst and Gneisenau in November 1939, and HMS Jervis Bay, which similarly sacrificed herself to save her convoy from the 11 in (280 mm)-gunned cruiser Admiral Scheer in November 1940.

[5] Some of these, together with others at ports around the wider British Empire, played an important defence role in World War II and remained in service until the 1950s.

A number of new similar guns with stronger barrels which allowed more powerful cordite charges to be used were manufactured for coast defence during World War II, and were designated 6-inch BL Mark XXIV.