Nice animation, but the cartridge doesn't drop in front of the bolt, it is pushed down at the front by the pressure plate while the stripper nose guides it out of the belt.
He doesn't have the feed pawls working correctly, and the bolt doesn't recoil far enough to be caught by the trigger lever, so it's a runaway as show.
I see that the guy doesn't take being corrected very well, so I thought I'd just post here and let it go at that.