Fort Bribie - the Guns
Guns of Fort Bribie - Bribie Island, Queensland, Australia

Some notes about the guns used at Fort Bribie.
The fort was built during WW2 as part of the Moreton Bay harbour defences.
Photos and research by Dr. Richard Walding.

If you worked there or have any feedback please email me:

Dr Richard Walding  
Research Fellow - School of Science
Griffith University
Brisbane, Australia

  • Fort Bribie Home Page
  • Royal Australian Navy Indicator Loop Station (RAN No. 4) 
  • Holidays on Bribie Island

  • Fort Bribie was defended with two 6" breech loaded Mark XI guns. Their gun histories tell an interesting story. When rearmament of the fixed coast defences was mooted, 6" dual role guns were chosen. Both the Royal Navy and the Royal Australian Navy had stocks of superseded 6" mark XI ("Mark Eleven") guns on P Mark VI mountings surplus to their requirements. Six-inch batteries were eventually installed at Signal Hill (Sydney), Breakwater and Illowra (Port Kembla), Cowan and Bribie (Moreton Bay), Emery Point and East Point (Darwin), Rottnest Island (Fremantle), Paga Paga (Port Moresby), Goods Island (Torres Strait) and Kupang (Timor).

    Six inch breech loaded Mark XI gun

    These guns and mountings were designed for naval service and had all originally been installed in destroyers and light cruisers as the main armament of larger ships. They were designed in 1905 and were first brought into service in 1906 after construction at Coventry Ordnance Works Ltd. in England. Their characteristics are listed below:

    Bore (calibre) 6" (152 mm) diameter
    Weight 8726 kg
    Length Overall 7.867 m
    Bore Length 7.620 m (300 inches). Hence 50 calibre (50 x 6")
    Chamber Volume 33.27 litres (2030
    Rate of Fire 5-7 typically (max. 12 in testing)
    Projectile weight High Explosive type (HE) - 45.3 kg (100lb)
    Propellant Charge HE (TNT) - 14.6 to 15.0 kg
    Bursting Charge HE - 6 kg
    Projectile Length HE - 58.2 cm
    Muzzle Velocity 895 m/s (2937 fps)
    Range 13085 m at 15 elevation (ship mounted); 16000 m maximum (coastal defence)
    P VI mount Training: +150/-150
      Elevation: -7/+20
    Total weight 18.3 tonnes (mounting, shield and "piece")