It is unlocked once Heather Mason kills God with a melee weapon; it will be available for the player to use upon beginning an Extra New Game. The player doesn't need to drain all God's health with a melee weapon - only the final killing blow must be from a melee weapon.
The unlimited submachine gun, just as the name implies, has automatic fire with unlimited ammunition. The weapon works quite well on most bosses, especially the Missionary and the Memory of Alessa, albeit using the unlimited submachine gun detracts from a 10 Star Ranking.
- Finding the unlimited submachine gun in the HD Collection unlocks the trophy/achievement "Heather's Got A Gun", the title likely being a reference to the Aerosmith rock song "Janie's Got A Gun".
- There is an audio glitch when firing the weapon in HD Collection, which produces an unpleasant sound distortion.
- Using this weapon on a Pendulum while it is airborne will cause the creature to move at incredibly high speeds, probably due to the rapid firing against the monster's blades.