The moat and ramparts have largely vanished, their stonework long since carted away, but the curved slot trench that allowed the guns to traverse, rotating on iron rails set into a shallow groove in the ashlar banquette, is still visible in the ground. A banquette, in fortification terms, is the raised step behind a parapet from which soldiers could fire over the wall. That this detail survives at all, while the earthworks around it have dissolved back into pasture, gives the site an oddly intimate quality: the mechanics of gunnery preserved while the defences themselves have gone.

The battery was one of six proposed for the Shannon estuary by a committee led by Gother Mann, Inspector-General of Fortifications, who in 1806 estimated the cost of the Carrig Island tower and battery at £6,000. The Board of Ordnance approved construction in 1810, though the project ran into early difficulties: a contractor named Flattery excavated the trenches but failed to complete the masonry work, and a second contractor, Quillan, took over and began building in 1812. By 2nd August 1814, master gunners had been posted to the completed batteries, with Robert Kinnerbury assigned to Carrig Island. Three years later, in 1817, the battery was recorded as holding six 24-pound guns and two 5.5-inch howitzers. Around 1868 the 24-pounders were replaced by heavier 68-pound smooth bore guns, and the position was finally abandoned in 1891. Together with the battery on Scattery Island roughly 2.8 kilometres to the north, Corran Point commanded both sides of a two-mile channel, meaning that any vessel attempting to pass upriver would have come under fire from opposite banks simultaneously. By 1837, the site had been repurposed as a coastguard station, a quieter function for a structure built with considerable military seriousness.

The rectangular bombproof tower, constructed of dressed stone, is the most complete surviving element. Its north face, 16.3 metres long, carries a semi-circular headed doorway with two pulleys that may have been used to raise a door or drawbridge-style barrier. The gun platform sits at roof level, reached by a staircase built into the thickness of the wall, a technique also used at the Kilkerin battery on the Clare shore. The south face is entirely blank, while the east and west sides each hold a mixture of large and small rectangular windows. Samuel Lewis, writing in his Topographical Dictionary of Ireland, described it as a battery and bombproof barrack for twenty men; the building was designed to absorb artillery fire, hence the battered, or slightly sloped, outer wall surfaces that deflect rather than absorb the impact of shot.