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Snipe/Knipe is certainly a surname found in the Kilrea area but McCahon (and its various spellings) is very common in both Kilrea and Co. Londonderry.
However, in this case the records for First Kilrea Presbyterian Church still survive and transcipts are online.
(see here to search for full details but beware as there are lots of mistakes-
www.torrens.org.uk/Genealogy/BannValley/church/contents.html)
1831 Margt- Joseph McAughey- Jane Snipe- Moyknock
1832 Nancy Jane- Joseph M'Aughey- Jane Snipe- Moyknock
1834 James- Joseph M'Aughey- Jane Snipe- Moyknock
1836 Sarah- Joseph M'Aughey- Jane Snipe- Moyknock
1837 Thos.- Joseph M'Aughey- Jane Snipe- Moneygran [this could be an error]
1839 Elizabeth- Joseph M'Aughey- Jane Snipe- Moyknock
1842 Joseph- Joseph M'Aughey- Jane Snipe- Moyknock
and-
1828 Joseph McCaughey witness at marriage of John? McNeill, Moyknock
1833 Joseph M'Aughey witness at marriage of Thomas Snipe & Margaret M'Aughey, Moyknock