Another time I operated a rifle in a dream. I was part of a Commando Team assigned to raid this one enemy installation and my job was to cover for the Team's withdraw to the Landing Zone where they would be picked up by helicopters and flown out. I was to provide cover and then escape and evade as best as I could.

Well, the main team was successful with its target, and causes so much confusion that the enemy were not certain where they went. They were angling off in the wrong direction. From my position, I took a few shots at some of the enemy pursuers, but then thought better of it. Since they were going in the wrong direction, I should simply let them go. My shooting at them might eventually tip them off that the escape route was more in my direction. Anyway, my shots missed, and with any luck, with the shot reports echoing off of various building walls, they would not know which direction they came from. I was able to slink off, and subsequently have perhaps my most important Lucid Dream.

But, again this illustrates that firearms in dreams can work well enough, but only if their use conforms to some actual duty, and even then, with a sense of responsibility and discretion.

Gratuitously mass murdering one's friends for the fun of it probably would not qualify.