E. Revenant posted:

This image conveys just how hosed her practices were on the set.

-The marked round with the nickel primer is the live round. It's amazingly easy to spot and should have been checked just because it obviously doesn't belong.

-Dummies with indented primers and ones with smooth un-indented primers are mixed up. Only indented primer dummies should be loaded into guns. The cosmetic dummy flat primer rounds should never be in a gun because they are indistinguishable visually from live rounds.

-I can't find exact testimony but set rumor is that she would load that tray and rattle the entire thing to check for blanks. No one is going to hear the one silent live round out of all the other rattling ones.

Also we now have Dave Halls testimony from just before the killing. He's the Assistant Director who plead guilty for not checking the gun that was handed off.

-Gutierrez the armorer brought the gun unloaded to the church and Halls verified that it was an unloaded "cold gun".
-Gutierrez then loaded the gun after she had an unheard conversation with Baldwin.
-Gutierrez went back the Halls and rotated the cylinder a few times so Halls could check for depressed primers but he didn't count so he doesn't know how many he actually inspected.
-Halls declared it good and Gutierrez handed the gun to Baldwin

There was no reason for the gun to be loaded with dummies for a practice take. It will be interesting what comes out on why she or Baldwin decided to load the gun.