A pipe bomb exploded in a farm shop building near Boardman, killing its builder, authorities said.The device was similar to, but smaller than, the improvised explosive devices that have killed American troops in Iraq, said Morrow County Sheriff Ken Matlack.Matlack said John Paradiso, 29, of Irrigon, was building bombs Saturday evening apparently to blow up vehicles so the metal could be sold as scrap. Local and federal investigators believe he was using gunpowder from old .50-caliber ammunition and bullet fragments.The explosion also ignited a second bomb, but it did not explode, Matlack said. Police found a third bomb, filled mostly …