In the Napoleonic wars air rifles were used as sniper weapons. It was regarded as "poor form" to use a rifle that was untraceable by smoke so anyone found on the battle field with an air rifle was summarily executed. The big bore rifles currently available will move a lot of lead pretty fast. My 35 cal will put a 158gr bullet through an inch of plywood. I never tried anything tougher. It's MOA at 75 yds. I can't see past that.
Don't forget Col. Sebastian Moran tried to pick off Sherlock Holmes with an air rifle.
