why does every story like this always contain the phrase "hit the forward assist"? Not to pile on with everyone else, but there is almost never a reason to push that thing. Seriously, I think people just thinks it looks cool to hit it at this point.
also, so many reloading mistakes here. I am sure your friend realizes all this now, but for anyone randomly reading this online, if you think you made some questionable ammunition; just pull it all apart. Definitely DO NOT go take it to a match or live fire training. And as one poster mentioned, visually check your cases for powder. Too much, and zero are both the wrong amount of powder to have in the case.
this reminds me of getting my motorcycle license and they talk about the "crash chain". It is usually not one thing that causes an accident, it is a series of small things all in a row.