A man who forced another to commit an armed robbery later raped him orally at gunpoint, a Melbourne court has heard.

The County Court was told the distressed victim ''couldn't back out'' and had no choice but to point a weapon at the face of a milk bar owner and robbed her of $700.

Prosecutor Louisa Dipietrantonio said that after the robbery, Hayden Byrne fired the weapon in a bungalow, reloaded it then pointed it at the victim's head and forced him to perform oral sex on him.

Ms Dipietrantonio said Mr Byrne forced another man, Nicholas Edmund Smith, to ''record'' the rape.

Smith later told police he filmed the act on a mobile phone but did not watch it.