Australian colonial forts see action by 1880s

OK, dunno if I've posted on this before- but during colonial times the colonial govts in NSW, Qld & Vic built forts to protect Sydney, Brisbane, & Melbpurne from any poss Russian naval incursions during the invasion scares of the 1850s- such as Fort Lytton here in Brisbane (which is where the 'History Alive' military living hist fair is held every yr). Of course, none of these forts ever fired their guns in anger- but what POD would be required for these forts to have seen action against foreign incursions by the 1880s ?
 
Well, you could have a situation where Britian intervenes in the ACW on the side of the Confederacy. Although a dedicated US attack is unlikely, the forts might be called into action against US ships in Australian Ports, say if they try to make a run for it if they hear of Hostilitys.

Or, i supose you could have the Catalpa Rescue go horribly wrong, which leads to a war in the Pacific between the Royal Navy and the US Navy, where a deliberate US attack/bombardment coould be possible.
 
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