Nathan James McRorie, 20, died in the lounge of an East Geelong home in the early hours of March 13, 2013, having spent time drinking alcohol and most likely using drugs, including ice, with friends.

But his inquest was told the gun that ambulance paramedics found near his body was tested and found to be not the weapon that killed him, and that the gun that did was never found by police.

Coroner Ronald Staines found Aaron Burnie - one of three others in the room when Mr McRorie was shot - most likely switched the guns and took the weapon that killed his friend.

The inquest heard Burnie was on parole at the time and left the scene with Maggie Cecic before paramedics arrived. Ms Cecic and Burnie's girlfriend, Bree Graham, were also in the room.

Mr Staines said the trio with McRorie had claimed the young man had made references to Russian roulette and had put a gun to his head and pulled the trigger.

The coroner said other people in the house ran into the lounge when they heard a gunshot and heard Burnie say "Nathan has just shot himself in the head", and "Why the f--- did you do that, Nathan?".

Mr McRorie's family made a submission to the inquest that he did not shoot himself and was instead the victim of a homicide.

Mr Staines said he had little confidence that the accounts of Burnie and the two women in the room were truthful or reliable.

But he said he had insufficient evidence to support the family's submission. "There can be a variety of adverse inferences drawn from the false, misleading and unreliable accounts given by the witnesses," the coroner said in findings handed down on Thursday.

"But inference of murder or homicide emerges as a less likely inference, such that these remain as unproven possibilities, rather than as probable."

The coroner found it was "more probable than not" Mr McRorie himself caused the gun to discharge.