What happens after you pull the trigger on a shotgun? - Answers

Assuming the gun is cocked, loaded, and the safety is off- Pulling the trigger moves the sear, which allows the hammer to be driven froward by a spring. It strikes the firing pin, driving the firing pin forward. This dents the primer of the shotshell, causing it to fire. The fire ignites the gunpowder, which burns quickly. Burning powder produces rapidly expanding gasses, which push the shot cup (holding lead pellets) up and out of the barrel. At the same time, the reaction to that pushes the shotgun back against your shoulder (kick of the gun)