It was a "gross breach" of Army regulations for an SAS sniper from Cheshire to have a gun and ammunition in his accommodation, a court has heard.
Sergeant Danny Nightingale, 38, is accused of having a Glock 9mm pistol stored in his wardrobe and 338 rounds of ammunition stashed under his bed.
The haul was recovered in September 2011 when civilian police searched the father-of-two's three-bedroom house, which he shared with another member of the SAS.
The court martial in Bulford, Wiltshire, has previously heard that the Army has strict policies governing the retention of weapons and ammunition.
Giving evidence, a special forces colleague of Sgt Nightingale said the rules applied to all service personnel, irrespective of their unit.
Prosecutor Timothy Cray asked the serviceman, who was known only as Soldier Y: "In your unit was there any statement for exception or turning a blind eye to these orders as far as ammunition is concerned?"
Soldier Y replied: "We have no dispensation nor have we had any."
Mr Cray asked: "Given the nature of your unit was there any special exemptions in terms of members of the unit having firearms for their own use that had not been issued by the unit?"
Soldier Y replied: "None whatsoever."
Mr Cray asked the witness: "The allegations against Sgt Nightingale are that he had an unauthorised firearm in his bedroom of his single service substitute accommodation and 338 rounds of live ammunition.
"From a unit point of view, if that were true, how seriously would such a breach be regarded?"
Soldier Y replied: "It would be regarded as a gross breach bearing in mind the nature and quantity of the ammunition that was allegedly found at the defendant's house."
The court room had been cleared and the public and press were able to watch proceedings from an annexe where they could hear Soldier Y's evidence but not see him.
Sgt Nightingale, of Crewe, whose regiment in court was listed as The Duke of Lancaster's Regiment (King's, Lancashire and Border), has pleaded not guilty to a charge of possession of a prohibited firearm, namely a Glock 9mm pistol, 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's family, including wife Sally and father Humphrey, were in court to support him