In 1597, he gave offence to government by assisting Sir James to fortify Dunluce Castle and took part in the defeat which the MacDonnells inflicted that year upon Sir John Chichester and the garrison of Carrickfergus.
On the accession of James I, MacDonnell, on 28 May 1603, received a grant of the entire district of the Route and the Glynns, extending from Larne to Coleraine, and containing 333,907 acres.