Stocks Fall, Bonds Rally After Weak U.S. Data --- Stocks unravel after factory report; Dow sinks 300-plus points -- U.S. stocks were hammered on Monday, with benchmark indexes falling through key support levels after a gauge of factory activity disappointed, heightening concern about the economy before Friday's monthly jobs report. -- Stocks had wavered ahead of the report that had U.S. manufacturing expanding at a substantially slower pace in January, driving overall factory activity to an eight-month low. -- "A report like this scares people ahead of the payroll number on Friday," said Andres Garcia-Amaya, global market strategist at J.P. Morgan Funds, who added the report's soft new orders component was of particular concern. -- Dropping below its 200-day moving average for the first time since Dec. 28, 2012, the Dow Jones Industrial Average shed 326.05 points, or 2.1 percent, to 15,372.80, with all but one of its 30 components in the red. - More, Kate Gibson, CNBC, at: http://www.cnbc.com/id/101384540