Lt Jonathan Price, 26, passed his live fire tactical training course among the bottom third of its 79 intake.
He finished the vital course with a B minus, a grade defined as performance to the standard expected “in most respects”.
Army chiefs passed him as “competent” while highlighting a range of shortcomings and concluded he needed “increased levels of supervision”.
The lieutenant was confronted with that conclusion yesterday and said he previously knew nothing about it and had finished the course “quite happy”.
However, within nine months of passing he was put in charge of a live fire army training exercise in west Wales, which went tragically wrong.
Michael “Mike” Maguire, 21, originally from Bantry, Co Cork, was hit in the temple by a shot probably fired by a fellow soldier attacking a target one kilometre away.
The shooting happened at the Castlemartin Ranges in Pembrokeshire in May last year.
Mr Maguire was standing in a designated administrative area, deemed secure, outside the range where live fire training was taking place.
An inquest jury in Cardiff has previously visited the military ranges and been told that soldiers shoot out to sea when training.
Activity was centred on two roughly parallel linked ranges which each have separate safe haven areas outside of where training occurred.
It is believed the machine-gun bullet which killed Ranger Maguire was shot from a training range next to the one where he was relaxing.
Lt Price, the regimental commanding officer (RCO), dismissed a suggestion that he failed to take on the responsibilities of a RCO.
The Vale of Glamorgan coroner, Mary Hassall, said evidence suggested the men in his command may even have been inadvertently shooting at each other.
She went through the training he underwent to qualify as the RCO running the range on the day and focused on remarks in his exam report.