Whose Magic Weapon for Cultivating Immortals Is the Automatic Pistol?

The protagonist was originally a battle-experienced special forces soldier who died accidentally during a dangerous mission. The soul traveled to a magical world of immortals. In this world, everyone is born with a magic weapon, and the protagonist's magic weapon is actually a 9mm automatic pistol with unlimited bullets. Due to his past life experience, the protagonist is extremely afraid of dying again, so he acts cautiously on the road to immortality, often using sneak attacks to win.