In addition to reconnaissance equipment, Almaz was equipped with a 23mm Nudelman rapid-fire cannon mounted in a stationary position to the forward belly of the station. This self-lubricating cannon was modified from the tail-gun of Tu-22 jet bomber, and was capable of firing 950 rounds per minute. Each 200 gram projectile flew at a speed of 690 m/s relative to the station. To aim the cannon the entire station would be quickly reoriented facing the threat.
Salyut 3/OPS-2 conducted a successful test firing on a target satellite remotely with the station unmanned due to concerns over excessive vibration and noise.
OPS-4 was to have featured two unguided missiles instead of the aircraft cannon, but this system has not been shown publicly and may have never been fully manufactured."