I saw this photo of Sarah Palin on Facebook today. It shows her shooting while on horseback.
We see people shooting while mounted all the time in the movies and on TV. We take it for granted.
What you may not know is that it is a huge effort to teach a horse not to totally freak out and lose it's shit when a gun goes off.
I knew a guy long ago that was a horse trainer for mounted police. He had a paddock at the end of an airport runway. There was also a propane device that went off randomly like a cannon.
The older horses helped teach the new horses.
It took a while until the horses got use to the noise. They would eventually ride them in the noise, then finally fire a gun without getting thrown.
--Eventually they don't even flinch.