An investigator and an officer both changed their evidence in the case of a soldier's death at Deepcut barracks in Surrey, an inquest heard on Tuesday.
Pte Collinson's parents said their son was happy with his life
Sgt Linda Dunford and Lt Gerard Hardy both gave statements about the position of the rifle after Pte James Collinson, 17, of Perth, Scotland was found dead.
The inquest heard both changed their evidence after seeing photographs.
It follows inquests into the Deepcut deaths of three other soldiers from Sussex, Wales and County Durham.
The inquest jury had heard Pte Collinson had been on guard duty, unarmed, in March 2002, when he apparently borrowed a colleague's rifle and walked off for a cigarette near the perimeter fence.
Shortly afterwards, a shot was heard and he was found dead.
Sgt Dunford, from the Royal Military Police Special Investigations Branch, gave a statement three weeks after the death saying she recalled the gun had been lying on the soldier's right-hand side with the barrel pointing to his head.
She changed her evidence after photographs showed it lower down and pointing to his feet.
Lt Hardy, an orderly officer on duty that night, said three months after the death the weapon had been on Pte Collinson's right-hand side.
Clockwise from top left: Sean Benton, James Collinson, Geoff Gray and Cheryl James
When shown the photographs, he also said he was mistaken.
Lt Hardy told the hearing it was against procedure for a soldier to borrow a colleague's weapon.
The inquest is being heard by Surrey coroner Michael Burgess who handled inquests into the deaths of Pte Sean Benton, from Hastings, Pte Cheryl James, from Llangollen, and Pte Geoff Gray, from Seaham.
The findings of an independent review into the deaths, between 1995 and 2002, are expected to be published by Nicholas Blake QC after this inquest.
Surrey Police's investigation was criticised in a review by Devon and Cornwall Police.
The families of all four soldiers continue to demand a public inquiry.