A Canberra man accused of using a gun during an alleged sexual assault has been denied bail in the ACT Magistrates Court.

The 19-year-old man, is facing 10 charges including rape, assault, confining a person and possessing a prohibited firearm.

The court heard the alleged incidents were spread over several days.

The pair had been a couple, but had split — reuniting briefly just before the alleged offences..

Court documents outlined claim the pair began arguing during a drive to the home of the woman's parents, when the man is alleged to have driven down a dirt road, where he produced a gun and made a threat to shoot her and then himself.

The woman told police he later calmed down and put the gun away.

A few days later when the couple were together at the man's Gungahlin home, the woman claims another argument erupted over her ex-boyfriend.

She said he became angry when she revealed she had slept with the other man after splitting with him.

The woman said at one point she went into the laundry and emerged to find the man pointing the gun at her and demanding she use it in a sex act.

He is then alleged to have committed the sexual assaults using the gun as a threat.

The woman said he later took her to the shower and washed her, telling her he loved her, before leaving her in the house while he went out with some friends.

The woman said she fled the house, seeking help from a neighbour, who urged her to tell police.

Alleged victim complied in fear, court told

She told police she complied with the man's alleged demands, as she was fearful she would be hurt otherwise.

Prosecutors told the court the facts were confronting, and the risks were real and unacceptable if the man were to be released.

Magistrate Robert Cook agreed, noting the significant number of charges, saying he was particularly concerned about the allegation the man had an illegal firearm.

The man told the court: "They've seized it."

But Mr Cook said that made little difference.

"That does not remove my concern you might get access to another one," he said.