Morrison Gunn, born c. 1758
Morrison may have been six foot three inches.
It is supposed he joined the Second Battalion of the then 73rd Regiment - Lord Macleod’s Highlanders – on the basis that his brother joined the First Battalion and it is supposed that Morrison died at Gibraltar whilst part of that Second Battalion. These suppositions seem to originate from this story - ‘Morrison died of consumption, immediately after the siege of Gibraltar which he went through. He was most anxious to return to his native land as soon as the fortress was relieved, but his Colonel seeing that he had only a few days to live refused leave… The 2nd (Battalion) came home from Gibraltar in 1783…. Rev. Archibald Gunn, New Brunswick, Canada…says that the chief died not of consumption but of his wounds’. 
I think the whole Gibraltar idea is wrong. A Morrison Gunn was gazetted as a lieutenant from the war-office on 24 July 1779 to the Sutherland Fencibles which was raised in February 1779. The Fencibles recruits were from the Sutherland Estates. It was officially formed at Fort George (near Inverness) in February 1779 and then served at Edinburgh until it disbanded in 1783. It was a sort of ‘home guard’.
I suspect this Sutherland Fencibles lieutenant was ‘our’ Morrison Gunn as there were very few Morrison Gunns, the Sutherland Fencibles came from the Sutherland Estate where Morrison lived, Morrison had the example of his older brother joining the real army (an expensive occupation) and Morrison needed a job as the family no longer owned Estates as money had run out, especially after William’s commission had been bought. As well, the Sutherland Fencibles works with the being ‘refused leave’ of the original story; you could get leave from Edinburgh or Inverness far more sensibly than from war-torn, isolated Gibraltar. Also, this was the second incarnation of the Sutherland Fencibles, so supporting the use of ‘2nd’ in the original story. It is to be regretted that the records of the 2nd Sutherland Fencibles are minimal.
The Gibraltar story fails in its own right -
It is most likely, therefore, that Morrison died from consumption (given the lack of glamour of the death I suspect it may have a real origin), in Scotland, sometime after being commissioned on 24 June 1779 but the exact date – and cause - of his death is not known. Given William died 10 September 1780 it is not clear that Morrison was ever the most senior of the MacHamish line.
 Page 193, M. R. Gunn
 Page 196, M. R. Gunn
 The Great Siege of Gibraltar lasted 24 June 1779 – 7 February 1783.
 http://clangunn.weebly.com/thomas-sinclair-supplement-4-23-12-1902.html accessed 2 April 2018.
 http://www.electricscotland.com/history/sketches/highlandsketches91.htm accessed 2 April 2018.
 Page xii, R.H. Burgoyne, Historical Records of the 93rd Sutherland Highlanders, 1883 London, Richard Bentley and Son.
 https://www.archive.org/stream/historyofscottis02kelt#page/596/mode/2upaccessed 2 April 2018. Or http://www.electricscotland.com/history/scotreg/macleod/1777.htm
 http://www.electricscotland.com/history/scotreg/macleod/1777.htm accessed 2 April 2018.
 For example, John Drinkwater’s 1785 published A History of the Late Siege of Gibraltar. He was a member of the 72nd Regiment.
 Lord Lyon http://www.lyon-court.com/lordlyon/files/Gunn,%20Michael%20James%20-%20Interlocutor%20and%20Note.pdf accessed 1 April 2018 provides a date of 1 May 1785 for Morrison’s death; this seems unlikely. If the Gibraltar story had been true then Morrison needed to die before May 1783 when his battalion returned from Gibraltar. The Sutherland Fencibles had been disbanded in 1783. Some supporting evidence is required to accept Lord Lyon’s seemingly random date.