State police originally charged Winmar with possessing a firearm as a prohibited person - an offence he has since admitted to.

Officers allegedly found recordings of Winmar with the gun in the lead-up to his girlfriend's death, with one showing him mimicking firing the gun out of a car, a detective told the Melbourne Magistrates Court on Monday.

Police claim he had shotgun cartridges and homemade guns, and the handgun was faulty when his girlfriend threw it towards him or at him, leading to it going off and killing her.

They have since charged Winmar with negligent manslaughter, some 10 months after his girlfriend's death.

Police allege he was negligent because he did not secure the loaded handgun.

The 29-year-old's barrister John Lavery said his client explained to authorities his girlfriend's death was a "terrible, tragic accident".

“He was clearly upset, distraught at the events that had taken place," Mr Lavery told the court on Monday.

He argued Winmar should be granted bail given he had already been on it for about nine months.

During that time Winmar has abided by his bail conditions and received counselling after he told police he consumed methamphetamine and alcohol before his girlfriend's death, Mr Lavery said.

Winmar possessed guns at the time of the fatal incident out of stupidity, and made them as "an experiment", the barrister said.

Winmar is an Aboriginal man who most recently worked in a factory for about four months.

“(The handgun) wasn't a drug dealing weapon, it wasn't anything of that sort - it was something done because of an interest," Mr Lavery said.

Magistrate Andrew McKenna agreed to grant Winmar bail on conditions including he continued to report to police three times a week and stayed at his home in Collingwood.

Winmar is next due before court on April 29.