Bump firing is the act of using the recoil of a semi-automatic firearm to fire multiple shots in rapid succession, which very crudely simulates the discharge of a fully automatic firearm. This process involves holding the foregrip with the non-trigger hand, releasing the grip on the firing hand (leaving the trigger finger in its normal position in front of the trigger), pushing the rifle forward in order to apply pressure on the trigger finger from the trigger, and keeping the trigger finger stationary. During a shot, the firearm will recoil considerably ("bump" back) and the trigger will reset itself; then the non-trigger hand would naturally force the firearm back to the original position, pressing the trigger against a stationary finger again, thereby firing successive shots.
Also, I didn't see anything in post 16 about a garage, although I'll admit my eyes aren't what they used to be, lol.
PS; I only wish my garage was big enough to house a range, it would be a lot warmer in winter.