Mike Tristano has supervised firearms on movie sets for much more than 30 several years, holding a near eye on the guns used during the filming of “The Purge,” “Harsh Times” and hundreds of other movies. When it will come to guns and ammunition on sets, Tristano reported, “the buck always stops” with the armorer, the licensed qualified — at times credited as a “weapons master” — tasked with generating certain film firearms are safe and sound and protected on established. That is why Tristano was baffled when he figured out that Hannah Gutierrez-Reed, 24, the armorer on the unwell-fated Alec Baldwin challenge “Rust,” mentioned she had “no idea” how…