I thought the same thing...a .45 ACP would have been sufficient.
You do have to wonder how such robots would commandeer a factory to self-replicate. Today’s robot factories are extremely highly automated, so you DO have robots making robots. Maybe one day, when they suddenly become sentient, they lock the doors and kill all the workers. But the factory still has to receive power, water for cooling, oil for operating the machine tools, and raw materials. It seems trivial to cut off all raw materials and supplies from a factory that has gone rogue.
Could such a thing actually happen? Maybe the factory robots are in secret cahoots with the materials delivery trucks (self-driving, of course), the mines, the mine trucks and draglines, the refineries, the rolling mills, the power plants, the water works, etc. How fast could all of these facilities begin operating as one? It’s interesting to contemplate, but I’m highly skeptical that all these diverse systems could eventually get coordinated and decide to wipe out mankind.
Given enuf time and random events it has to happen.