Multiple sources directly connected to the ‘Rust’ production tell TMZ … the same gun Alec Baldwin accidentally fired — hitting the DP and director — was being used by crews members off set as well, for what we’re told amounted to target practice.

We’re told this off-the-clock shooting — which was allegedly happening away from the movie lot — was being done with real bullets … which is how some who worked on the film believe a live round found its way in one of the chambers that day.

Obviously, authorities would want to speak to anyone who had been using the weapon for target practice, and — more importantly — to whoever was putting the gun back among others used for filming.