That is a picture of an 1863 Springfield Rifle. The 1863 model Sprinfield Rifle fires a .58 caliber bullet that leaves a fist-sized exit hole in a human body. One could argue that people using this gun, or ones similar in design, killed more Americans than with any other weapon. It was the "assault rifle" of its day.
In the hands of a semi-skilled marksman, it can put a fatal hole in a human from three football fields away. Even given the slow rate of fire, with a little practice, there is time to shoot you a second time if you started running at the shooter after the first shot.