Lower Georges Heights Commanding Position

The Lower Georges Heights Commanding Position was constructed and designed to stop enemy ships from entering into Sydney Harbour, and worked in conjunction with several others forts located within close proximity.

In contrast to smooth bore cannon which preceded it, the rifling of the gun barrel allowed much greater accuracy and penetration as the spin induced to the shell gave it directional stability.

Initially smooth-bore cannon were converted into rifles by re-boring and lining; but later new guns were manufactured from scratch as RMLs.

The RML 9 inch 12 ton gun could discharge shells weighing 249 pounds (113 kg) as far as South Head (Watsons Bay); approximately 3,000 yards (2,770 metres).

As technology improved, these cannons were replaced in 1889 by much lighter weight guns that could fire an 80-pound (36 kg) projectile for 3,170 yards (3,000 metres).