The BL 9.2-inch Mk IX and Mk X guns were British breech loading 9.2-inch (234 mm) guns of 46.7 calibre, in service from 1899 to the 1950s as naval and coast defence guns. They had possibly the longest, most varied and successful service history of any British heavy ordnance.

Breakneck Battery is an artillery battery in the British Overseas Territory of Gibraltar. It is located on Ministry of Defence property at the Upper Rock Nature Reserve, north of Lord Airey's Battery. It is one of a dozen batteries in Gibraltar that had 9.2-inch (233.7 mm) guns installed around the turn of the twentieth century. The emplacement features a 9.2-inch Mark X breech-loading gun on a Mark V mounting. The battery was refurbished by 10 Signal Regiment in 2012 and 2016 whilst being on Ceremonial duties whilst the Gibraltar Regiment where on exercise and is one of three surviving 9.2-inch gun emplacements at the Upper Ridge of the Rock of Gibraltar. By the late twentieth century, the 9.2-inch guns in Gibraltar, Bermuda, Portugal, South Africa, and Australia were the remaining examples of an emplacement that at one point had been mounted at strategic locations across the British Empire.