SAS sniper 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.
The 38-year-old has been on trial at the court martial centre in Bulford, Wiltshire, for the past week.
The haul was recovered by civilian police in September 2011 in the rented house the father-of-two shared with another SAS soldier, known only as Soldier N.
The pistol was found in Sgt Nightingale’s wardrobe and the ammunition was under his bed in a plastic box.
Sgt Nightingale, of Crewe, has pleaded not guilty to possession of a prohibited firearm between November 26, 2007 and September 16, 2011.
He also denies possession on or about September 16, 2011 of ammunition, namely 122 9mm live rounds, 40 7.62mm live rounds, 50 9mm frangible rounds, 50 .338 armour piercing live rounds, two .308 live rounds and 74 5.56mm live rounds.
Sgt Nightingale said he had no knowledge of the Glock and ammunition being in his bedroom and said they were put there by someone else.