The finding of gross negligence / manslaughter seems too extreme, to me at least, especially given the time elapsed - some 34 years after this tragic event. It is all too easy to produce an unsafe conviction, even without a defined statute of limitations in UK law.
It is beyond any doubt that this teenage soldier influenced in any way the preceding events leading to this fatal outcome. Political decisions put soldiers on the streets of its citizens and to arm them with battlefield weapons such as the belt-fed heavy GPMG used here. All the operational commanders and tactical leaders of this junior soldier have long since died, taking those who sited the sangar, defined the arcs of fire and detailed a loaded GPMG for that role on that street. With all those actual decision makers now dead they are removed from the witnesses-for-the-defence list, cannot be cross-examined or account for their own actions. Above all, all those decision makers knew and accepted the additional risk to human life when you put battlefield weapons in that situation. When they 'accept' that risk they 'own' part of it. It should not all tumble down to the last soldier and certainly not to the extent that a careless disregard for life is attributed to him alone.
The elapsed time also robs the accused of any detailed memory of his actions or those expected of him. I may have spent most of my own career flying but I did do 3 brief stints in supporting specialist roles which required me to deploy fully trained and current on the GPMG. My last time behind this weapon is 'only' decade ago and even in that shorter timespan I cannot recall all the drills and quirks of the GPMG. I do remember that the drills changed between my first and second qualification (feed tray) and varied again for helo use. For those in the US reading GPMG = M249 you would be very close but all the extra safety revisions and the drastic removal of the number of risks of an ND have never been retrofitted to the British GPMG. I've had a US colleague grab my arm in the dead of night when he saw me operate the cocking handle before removing the belt and my 'failure' to conduct drills with the safety applied - but that was (is?) required of our rustic / original 'version' of the modern M249.
The British version of the FN MAG / GPMG is an awesome battlefield weapon but it is not a weapon you would want on your own civilian streets. It has zero design sh*** given for accidental firing (negligent discharge), just to spit hate at HMG's enemies. With a safety that cannot be applied unless cocked, fixed firing pin on an open bolt action, no traverse safety blocks/sears, normal drills conducted with the safety off, fully cocked for an 'unload' to remove the feed-horn pressure on the first round, feed tray drills slowly swapping from sweep alone to actually checking the breach for a live round before changing back again, depending on where the decision wheel was, using the trigger on normal drills, slip-fire risk with the top cover, an 'unload' drill that accepted that a live round could remain in the breach and be fired when you pull the trigger during the 'unload' drill... etc etc. No doubt those with better memory can correct, add or even take away from the list but the point is that these risks would be unacceptable for weapon acceptance now and even back then the risks were held by the MoD, not the soldier alone.
So we grab a junior soldier from basic, train him hard for ceremonial duties with his trusty SLR and shiny boots n' bayonet before a quick refresh and deployment in NI, with an unforgiving and loaded GPMG in a UK domestic street. Things can go wrong and the soldier has the final part to play - everything else that suggests an 'indifference to life' should sit at a level way-higher than the individual soldier.
Of course, none of this detracts from the unacceptable death in this incident; the victim was going about his day-to-day life before being hit once by a crazy-angle ricochet from an accidental 3 round burst from a battlefield weapon that was not aimed or pointed anywhere near him. The Crown put that soldier in that spot, with that weapon and in doing so it accepted its part in the increased risk to life. The Crown should not absolve itself 34 years later and then place all the blame on a single teenage soldier operating in a very different time to that of the modern day.