Thank you. I normally do all this when riding her. I say a horse is never Bomb Proof, a new rider, new trail and that horse can spook. If I feel uncomfortable or feel like she's tense because of something she sees or hears I will start the circles, backing, I feel it it makes me relax and her.
I just got a laugh at seeing my girlfriends face when I yelled boom boom boom. Haha
Minimon, what worked was that you gave them a distraction. Horses usually settle fairly quickly with repetitive sounds, that of the gun. To help prevent spooking, don't allow the horse time to think about spooking but keep his mind busy on what you are asking so it's a constant serpentines, circles, backing, even partially doing these so you are constantly bending the horse and moving the hind quarters.