The New York Times used sonification along with a dot plot to demonstrate the speed of gunfire in Las Vegas. They compared it to the shooting in Orlando and an automatic weapon.
It is possible that the Las Vegas gunman modified his gun to fire faster. This could include using a trigger crank, a mechanical add-on that is rotated like a music box handle and hits the trigger multiple times per second. Or, he may have had a bump fire stock, which uses the recoil of the rifle to fire quicker. Neither device is regulated by the National Firearms Act.