The new acting director of the Bureau of Alcohol, Tobacco, Firearms and Explosives announced a major shake-up of his agency Wednesday and urged Washington insiders to “calm down” about the latest revelations surrounding a controversial ATF gun operation. B. Todd Jones said calm is needed as he begins rebuilding the beleaguered agency, including shuffling top personnel. He made his comments as his boss, Attorney General Eric J. Holder Jr., came under fire this week from Republican lawmakers, with one calling for a special counsel to investigate Holder’s role in the Fast and Furious gun-trafficking operation.