Sergeant Danny Nightingale, 38, a special forces veteran who has served more than 18 years in the military, is accused of possessing a Glock 9mm pistol and 338 rounds of ammunition.
Sergeant Danny Nightingale and his wife, Sally
A court martial at Bulford, Wiltshire, was told that the handgun and ammunition were recovered when civilian police searched the father-of-two's accommodation, which he shared with another soldier, known only as Soldier N.
Timothy Cray, prosecuting, told the five-strong court martial board: "The Crown's case put shortly is that the defendant's possession of the firearm and ammunition was in breach of standing orders that are familiar to every soldier and fundamentally was contrary to the law of this country.
"We say there is no excuse for what the defendant did.
"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."