Hi Bitzar,
The primary source for Imperial soldiers who took their discharge in New Zealand is H & L Hughes' Discharged in New Zealand (1988), compiled from regimental Muster Lists.
I have searched my CD-ROM copy of this title but there is no mention of a John MCCARTHY of the 18th Regiment taking his discharge in New Zealand. My own research has discovered several omissions from this title.
Does any of the information you have collected mention where he took his discharge? Might it have been Australia? If is what indeed New Zealand he might be another omission from Hughes' work.
I quote from the introduction for the 14th Regiment given on page 19 of Discharged in New Zealand.
"2/18th (ROYAL IRISH) REGIMENT
The 18th Regiment ("Paddy's Blackguards") formed a second battalion in
Ireland in 1858; when it was up to strength it moved to Aldershot (1859) and
later Portsmouth (1861) before going to the Channel Islands in May-June 1862.
It is interesting to note here the rates of pay applicable to the army at this
period; a Sergeant Major received 3s2d per day, Colour Sergeant 2s6d, Sergeant
2s, Corporal 1s4d, Private is and a Boy 10d. The battalion Schoolmaster got 4
shillings a day, but the 'Schoolmistress, 3rd class' only received 24 pounds
per annum.
In February 1863 the battalion moved to the Isle of Wight preparatory to
embarking at Portsmouth for New Zealand. On arrival at Auckland the 2/18th went
first to Otahuhu camp and then took part in various engagements along the route
of the Great South Road, eventually culminating in the action at Orakau (MarchApril 1864). After a brief return to Otahuhu the regiment sailed from Onehunga
to Wanganui early in 1865 and stayed in that area until November 1867 when they
returned to Auckland, except for two companies at New Plymouth and two sent to
Napier. In February 1870 they sailed for Australia, being the last Imperial
Regiment to leave New Zealand, and later that year they arrived back in England.
In the list of discharges an asterisk after the regimental number indicates
a soldier on the Married Establishment, recorded from April 1868; their marital
details are on page 22. It is interesting to note that in July 1869 the list
showed a total of 92 wives (12 of them named 'Mary Anne') and 238 children."
Spades