Finding information in Northern Ireland is very difficult. The best source is the Public Records Office Northern Ireland, PRONI. With patience you can dig out fragmentary information. However, Andrew McKown does not appear in any records that I could find. Also, there are no Gilberts in the right time frame. Keep in mind that records only exist from a few parishes for very few years, so this chances are hit and miss, mostly the latter. There were McCowans in both Counties Antrim and Down. The name was spelled many ways. I will be back there sometime this fall as a side trip to a business trip. Hope springs eternal.