Ouchers.
The first time my mom fired a gun it was a shotgun...my dad's 10gauge. Even though she'd been told MANY times to hold it tight against her shoulder just before she fired she pushed it out about two inches off her shoulder. The impact knocked her flat on her back where she promptly discharged the second barrel into the roof of the shooting hut.
My dad says it would have scared everyone in the place silly if they hadn't all been laughing so hard. She was horribly bruised over her whole chest, shoulder, arm, and even onto her back.