Their role was to man coastal defences and fortifications, relieving the Royal Artillery (RA) for active service.

The first Lieutenant-Colonel Commandant was John Skeffington, 10th Viscount Massereene, KP (1812–1863), and the headquarters was established at Carrickfergus Castle.

[5][6][7][8] Carrickfergus Castle's obsolete guns (6 × 64-pounders, 7 × 32-pounders and 1 × mortar, with an additional 6 × 24-pounders from 1859) were used for training, and the 64-pounders were fired on 27 May 1856 to salute the peace at the end of the Crimean War.

[7] Clotworthy Skeffington, 11th Viscount Massereene, (1842–1905), the eldest son of the first commandant, was appointed Lt-Col on 20 November 1872, having served as major since 5 August 1865.

[6][7][21] Lieutenant-Colonel Pottinger had been the Antrim's CO since 11 October 1890, and Maj Elmitt Instructor of Artillery since 27 February 1892.

[8] The company's duties included escorting Boer prisoners of war to St Helena, and improving the defences of the Cape Peninsula and the Orange River Colony (ORC).

At the end of September 1900 a detachment of 25 Antrims joined a similar number of Donegals, all under the command of Capt F.H.

[6][7][21] The brigade left Cape Town for home in June 1901, having been relieved by the Norfolk Artillery Militia.

[6][7][22] In addition, Lt-Col Pottinger was awarded a CMG and CSM McCabe a DCM.

There were moves to reform the Auxiliary Forces (Militia, Yeomanry and Volunteers) to take their place in the six Army Corps proposed by St John Brodrick as Secretary of State for War.

[24][25] Under the sweeping Haldane Reforms of 1908, the Militia was replaced by the Special Reserve, a semi-professional force whose role was to provide reinforcement drafts for Regular units serving overseas in wartime.

[7][29] The Antrim RGA manned two Vickers-Maxim Mk VII 6-inch guns at Grey Point Fort, a new battery built at Helen's Bay on the south shore of Belfast Lough between 1904 and 1907.

[30][31][32][33] At the outbreak of war the Antrim RGA had a strength of 607 all ranks, but as the war progressed and the likelihood of German attacks on the coast diminished, the Special Reserve's role of supplying and training reinforcement drafts for fighting units of the RGA took precedence.