Nice job on the video. You do an excellent job and have a good presence unlike many of us doing videos. You need to come down some time to Texas and do video with my Swedish BAR and Stoner 63A system, been planning on doing one for a while just have not gotten around to it.
I like the PKM as well except for, as you found out, the ejection is very violent and injuries the shooter if they are not careful.
One item you might think about next time you do a video if an open bolt LMG, the charging handle should be push back forward before firing the gun. Otherwise energy is removed from the system and can lead to malfunctions. Of course the PKM has a recoil spring that will drive a nail. Also it induces more wear on the charging handle slot and the tab on the bolt carrier that interfaces with the charging handle.

