I would expect that the load for a shot at the camera, these days, would be 5 dummies and 1 properly positioned blank. With the high resolution today’s movie-viewers expect, the dummies have to be there. The blank will give all the reality you need without stupid CGI.
With this kind of load, the actor could not realistically check without ruining the shot.
Baldwin was, no-doubt, lazy. For a rehearsal with what should have been empty or all dummies, he could check - click, click, click 6 times.
Of course, anyone there watching would know how he operates, and there is the final, filmed shot, where as I said, I don’t think he can check.
Yes, you are right about the dummies for realism, but it is very rare that a blank is fired directly at the camera. You would use a full load dummy rounds for pointing the gun at the camera, or pointing it and pulling the hammer. That could be a threatening gesture. If there was an intent to show the gun shot, then there would be a cut right before the gun was fired, or CGI used.