I hadn't heard any of the stories about the crew using prop guns for target practice but if true this is industrial strength stupidity which puts a huge liability on the production company for allowing this to happen.
This Hot Air blogpost by Allahpundit summarizes and puts together a lot of what is "known" and analyzes its meaning. Allahpundit is my least favorite Hot Air writer, because (s)he is Never-Trump to an over-the-top degree, and on some issues (s)he is less than well-informed and/or makes things less than clear.
BUT in this piece (s)he really puts a lot together and is clear about the implications.
Among other things, (s)he explains why, in the normal course of how things are done, it would have been very unusual for Baldwin to check the gun personally. On the other hand it is very clear the as the producer responsible for hiring capable, safety-conscious (not just gun safety) people, Baldwin failed horribly. And Baldwin failed to take steps to rectify obvious, dangerous, safety issues.
At this point, then, it looks like the Armorer and First Assistant Director may be on the hook criminally, while Baldwin should get clobbered in civil court for his choices and failures to act as producer.