Colonel Charles Barnett, from the Services Prosecuting Authority, said outside the court:
Sgt Nightingale has now had the trial which he requested, which is his right to seek. He has now been convicted by the board.
His fine record as a soldier is a matter that will no doubt be considered carefully when the board considers his sentence.
Sergeant Danny Nightingale has said that he is still struggling with a brain injury he received during an endurance marathon in 2009.
He said "there are now things in my head that are not facts" and added that he sometimes had difficulty recognising his own family members.
His wife Sally added: "He never brought a weapon into the country ... He still confabulates and still struggles with his brain injury on a day-to-day basis".
Much of Sgt Danny Nightingale's court martial rested on conflicting accounts of how the gun and ammunition came to be in a home he was staying in.
- The prosecution accuse him of changing his story. He allegedly told police that the gun had been a "trophy" given to him in Iraq and that he had accumulated the ammunition from training sessions in the UK. Nightingale later told the court martial that someone else had put them there.
- The defence allege that Sgt Nightingale's memory was affected by a brain injury and that his confession to police was false because he was "confabulating" (filling in gaps in his memory based on what other people had told him). He said he had "no recollection of receiving the gun".
Asked whether he planned to fight on for his proclaimed innocence, Sergeant Nightingale said he had to ask the question: "Realistically can we keep going?".
He said that he had concerns about the "longevity of the family".
The solicitor for Sgt Danny Nightingale has tweeted that the family will be seeking advice on whether to appeal against his conviction by a court martial board for illegally possessing a pistol and ammunition:
the #nightingale sentence raises point of law of exceptional importance and has been referred to the Court Martial Appeal Court
the#nightingale family will now be seeking advice on an appeal against the convictions
Speaking outside the court martial, Sergeant Danny Nightingale has apologised to taxpayers for footing his ongoing legal battles.
He said that his own part in covering legal bills had been "financially debilitating".
- 2007: Returns to UK from tour of duty in Iraq.
- October 2009: Suffers brain injury during an endurance marathon in Brazil.
- September 2011: Civilian police discover the pistol and ammunition in Nightingale's rented home after a tip-off. He allegedly tells police that the gun was a "trophy" from Iraq, although he later contests this account.
- November 2012: Pleads guilty to gun offences and is ordered to serve 18 month in military detention. The Court of Appeal later reduces and suspends his sentence.
- March 2013: Original conviction overturned by Court of Appeal
- July 2013: Convicted of the original offences by a fresh court martial
During the course of the court martial, Prosecutor Timothy Cray accused Sergeant Nightingale of making a "series of mistakes" and of changing his story:
No soldier, no matter what his experience is or what unit he is attached to, is above the law.
On the specific facts alleged - that is, the defendant's attitude to the retention of arms and ammunition - is that he made a series of mistakes that put the public at risk and that is why he now comes before this court martial.
No matter how he tries to deny it, the gun and ammunition were there in his bedroom because he put them there and he kept them there.
The sentencing of former SAS sniper Danny Nightingale was adjourned today pending a Court of Appeal judgment on the sentencing powers of the court.
Judge Advocate General Jeff Blackett said he would release Sergeant Nightingale on bail while a decision was made.
Sergeant Nightingale was previously sentenced to 18 months' military detention at an earlier trial. This was reduced to 12 months' imprisonment, suspended for a year, on appeal.
Former SAS sniper Sergeant Danny Nightingale, 38, has been convicted by a court martial board of possessing a Glock 9mm pistol and 338 rounds of ammunition, which were found in his bedroom in September 2011.
Nightingale had originally pleaded guilty to the two charges in November last year and was sentenced to 18 months' military detention.
The father-of-two, from Crewe, Cheshire, appealed against that sentence. which was subsequently reduced.
The Court of Appeal later quashed Sgt Nightingale's original convictions and a fresh trial was ordered.