On entering the magazine there is a twelve metre tunnel which slopes down and to the right.
The Magazine was initially constructed for the Mark IV 9·2-Inch BL Gun once at this location. In the early 20th Century, the gun was removed and the emplacement above demolished and replaced with a new Emplacement to mount two 6 Inch QF Guns which were being moved down from Mount Siloso. The Magazine was was modified and enlarged to service these two guns. An extension was created on the left of the magazine to enlarge it for the two 6-Inch QF guns.
The modified Magazine was much as is seen today with the Ammunition Hoists in the same place. The QF Magazine held 1100 Shells and 1100 Cartridges. The date of commencement of work was given as being 30th November 1908 and completion on 30th September 1912. The cost of the conversion from a 9·2-Inch Battery to a two gun 6 Inch QF Battery was was £6,217. The Wartime BL Magazine held 1100 shells and 1100 Cartridges the same as the QF Magazine it replaced, but 100 of the shells were High Explosive.