http://online.wsj.com/article/SB10001424127887324235304578440843633991044.html
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Mr. Weimer of Phantom Fireworks in Youngstown, Ohio, said that his company believes that the quantity of powder in the fireworks wouldn't have been nearly sufficient to produce the Boston blasts. Each shell contains a small amount of explosive material, and some is used to produce whistles and other effects.
Mr. Weimer said extracting powder from the mortar kits "would have been a very long, involved process."
Much larger quantities of black powder and similar low-grade explosives can be purchased at gun stores and other outlets, he said, and would have been a simpler and cheaper way for the alleged bombers to procure explosive material.
"It's highly doubtful" the Boston bombers used consumer-grade fireworks, said Julie Heckman, executive director of the American Pyrotechnics Association, an industry trade group. She said it would take far more than 48 of the small mortar shells to produce the explosions seen in Boston.
Other experts, however, said people could make a bomb from such fireworks. "It's a rather primitive way to build an explosive device, but you could do it," said John Conkling, a chemist with decades of experience in fireworks. "You would also have a good chance of blowing yourself up.''
