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The "Disappearing Gun"

This gun is "disappearing" in more ways than one. Much of the barrel has since been removed and recovered as scrap with this specimen, but it is also clearly visible that the attempt was abandoned, but these guns were known as disappearing guns for another reason and the clue to this is the large circular enclosure where they were placed.

They were designed to be brought up over the lip of the circular enclosure, quickly aimed, fired and then the recoil would automatically drop the gun into the enclosure a long time before the sound or projectile even arrived at its target. There are numerous of these enclosures (and more complete versions of the guns) around the island.