A judge has criticised the Army for deploying a territorial soldier to Iraq with "deficient" weapons training.
Ian Blaymire was fined and discharged from the Territorial Army
Assistant judge advocate Paul Camp made the comment at the court martial of L/Cpl Ian Blaymire for the manslaughter of a fellow soldier in Iraq.
L/Cpl Blaymire was acquitted, but found guilty of breaching military discipline by failing to follow the correct safety procedures for weapon handling.
The Ministry of Defence said there was an "appropriate level of training".
As he discharged L/Cpl Blaymire from the Territorial Army and fined him £2,750, Mr Camp said: "The system in Iraq was very slack in weapon handling terms.
"You have been let down by the Army."
Sgt Nightingale was shot at point blank range
L/Cpl Blaymire, 28, had been accused of shooting his friend Sgt John Nightingale at Shaibah military camp, south Iraq, on 23 September last year.
His court martial was held at Catterick Garrison near Richmond, North Yorkshire.
Mr Camp said: "Your training was deficient, you shouldn't have been deployed without further training."
The judge also said his commanding officer had to "bear considerable morale responsibility for what happened".
Sgt Nightingale, 32, from Guiseley, West Yorkshire, died after being hit in the chest at point-blank range by a bullet from an A2 rifle.
He was a Territorial Army soldier with 217 Transport Squadron, part of 150 Regiment (Volunteers) of the Royal Logistic Corps, based at Churchill Barracks in Leeds.
L/Cpl Blaymire, a plumbing and heating engineer from Leeds, was a TA driver deployed as part of 150 (Yorkshire) Transport Regiment, Royal Logistic Corps (Volunteers).
He had taken a colleague's rifle to a troop office at the military camp and met his friend Sgt Nightingale, the court was told.
While in the office, Sgt Nightingale, who had passed his weapons test, pulled the cocking handle on the rifle and as L/Cpl Blaymire stepped back with the rifle it fired a bullet into his chest.
The court was told L/Cpl Blaymire, who had not passed his weapons test, did not realise there was a live round in the chamber and had not checked.
However, the five-member panel decided, after a 44-day hearing, that the shooting was a tragic accident and cleared him of manslaughter.
The court was told that at least 2,000 reservist soldiers should not have been deployed to the Gulf after failing weapon-handling tests.
After the sentencing on Wednesday, the Ministry of Defence said it would "consider very seriously the comments of the judge advocate".
"Our policy is to ensure that all our soldiers have the appropriate level of training required to fulfil their roles and operations," a spokesman said.
"Over 9,000 TA soldiers have successfully completed this training before deploying to Iraq.
"If there have been individual failings we will of course investigate and take appropriate action."
During the court martial, documents revealed that top secret plans for attacking Iraq were drawn up five months before the war started.