CHICAGO, Illinois (AP) -- A study has found that air rifles, paintball pistols and BB guns injure as many as 21,000 Americans each year, undermining the notion that such weapons are harmless in the hands of young people. Nonpowder guns kill an average of four Americans yearly, and from 1990 to 2000, there were 39 such deaths -- 32 of children younger than 15, according to a report in November's issue of Pediatrics. The report, published Monday, comes just two weeks after the BB gun death of an 8-year-old South Carolina boy accidentally killed by a 13-year-old friend. The pellet...