Cant blame the prop master as that person is not the weapons handler. On top of that, you have no idea how difficult it is to keep actors from playing with guns on set. You literally have to stand 1" off camera and be ready to pounce with some of these actors. Check into his death and how the on set manufacture of blank rounds and a non blocked barrel live fire pistol are at fault. I forget at the moment if it was a primer but an object lodged into the barrel from a prior scene, gun was not checked when it was unloaded nor when it was reloaded. On top of that, the 1st AD should check as well.