Sergeant Mossbruker carried a six-shot revolver the day he died. The bullets from that gun fit in the palm of my hand. Now here's the type of ammunition fired from Albert Petroski's .50-caliber rifle, some call it a sniper rifle. Each round is a half-inch wide and more than five inches long. This is the largest, most destructive round of ammunition legally available. Today, sniper rifles are enjoying their greatest popularity ever among civilians, and that has some people worried.