I found a gun like that once, it fired a spread of 3 purple bullets, IIRC. I was not a fan, but I think that's because it didn't home properly. The first couple of times I fired it, the shots went about an inch (size of my mech) and stopped. Not quite like the video, but not far off.
They also liked embedding themselves in walls, like they had wall-penetration, but would never actually get to the enemy they homed in on.
I never got any screenshots of the wonky behavior, however, because every time I went to try, it worked Just Fine.