

In Episode Two, it is found in a doorway in the chapter Freeman Pontifex, near a small overrun Resistance outpost. In Episode One, it can be found in a Combine supply room in the chapter Urban Flight. The player first acquires the weapon at the end of Half-Life 2's sixth chapter, "We Don't Go To Ravenholm.", scavenged off of a dead soldier previously fighting stray Zombies coming out of Ravenholm. While similar, the mounted variant, the Emplacement Gun, is a different pulse gun. Notably, a Rebel at White Forest informs his comrades that the weapon's secondary attack can be useful against Hunters, leading to the AR3 dispute. Rebels often capture OSIPRs for their needs. If the Overwatch Elite is killed, they will drop an Energy ball and the player can pick it up. While the OSIPR is common amongst the Overwatch forces, only Overwatch Elite are allowed to fire the Energy Balls. On the body can be seen the alphanumerics "V952", also featured on other Combine devices. A Dark Energy Ball shooter is built into it, in which the orb is capable of disintegrating almost anything it touches. Said magazine considered an optional upgrade in Half-Life: Alyx, suggesting the box magazine might be a more recent addition to the standard issue weapon design. It has a 30-round energy cells, which is reloaded with an automatic mechanism built into the weapon from the box magazine.

Rebel firing at the Hunter-Chopper in the Outlands with his OSIPR.
