Armstrong served as a part-time Royal Ulster Constabulary Reserve Constable for fourteen years from 1975 until 1989.
He is also a member of the Loyal Orange Order, holding the position of Honorary Secretary of Chambré's Volunteers L.O.L.
171, and a member of the Royal Black Institution where he currently holds the position of Lay Chaplain of Tamlaghtmore Red Cross Temperance R.B.P.
He currently serves as Deputy Whip of the Ulster Unionist Party Assembly Group, and is the UUP Spokesman for Social Development.
[5] Armstrong's office is a prefab, which stands beside his home, Prospect House near Stewartstown, County Tyrone.