The AKMS is the main variant of the AKM, a 7.62mm assault rifle.
Terminator 3: Rise of the Machines
One of the weapons taken from the coffin is an AMKS with a chopped barrel and two magazines held together with a dual-mag clamp. John Connor is first seen using it, trying to defend himself from the T-X when she boards the Hearse he and the other two are making their escape from the cemetery in. It then appears several more times at Cyber Research Systems, most notably when Katherine Brewster uses it to destroy an HK-Drone, and then when it's yanked out of Connor's hand by the electromagnet that attracts both the gun and the murderous T-X to it.
The AKMS was being used by a Tech-Com soldier during Operation Chrono.
- In Terminator Genisys, the Plasma rifle being used by Tech-Com soldiers, including Kyle and John, is apparently based on AKMS. But is referred to as a PK-47 in Terminator Genisys: Revolution.