“AB was screwing around...”
I think THAT is the essence/crux of the situation.
He’s totally culpable for his actions.
There are implications for insurance coverage in the incompetence of the armorer, or the sabotage of the loadings. Solid chain of custody would have prevented sabotage. If it’s all on Baldwin, why have an armorer and an AD in the chain? To save time? Why not have one or the other come out and hand an open gun and six blanks to AB?