I wouldn't be so bold as to call this a "test video," but I did take my new gen PMAGs to the range to see if I could induce a failure. The only problem I've had with any standard 5.56 mag related to the 300 BLK has been when a loaded mag has some sort of impact, making a mess of the rounds in the stack. This happens mainly when I load 220gr subsonics, and it makes sense. The bullets are 4x the weight of XM193 bullets, making the mag spring work extra hard to keep everything in the box organized and happy.
The Gen M3 has a few big changes to the follower and spring base plate. There are also subtle differences to the internal ribs. It my brief testing, I had a hard time getting the rounds to bind up in the new PMAG like I occasionally have happen in the 2nd gen PMAGs. In any case, other than spitting a few rounds out of the top, these mags performed flawlessly for me with both 220gr subs and 115gr supers.
Two other observations:
1. I had no problems seating these mags with my Mega Arms Ambi Billet lower. This was mentioned by Stickman before, but I personally confirmed that a regular guy won't have issues, either.
2. This is one of the coolest videos of suppressed 300 BLK that I've done so far. Subs and supers sound phenomenal in the rapid fire mag dumps.