 The impracticability of a gun-type bomb using plutonium was agreed at a meeting in Los Alamos on 17 July 1944.All gun-type work in the Manhattan Project was directed at the Little Boy, enriched-uranium gun design, and the Los Alamos Laboratory was reorganized, with almost all of the research focused on the problems of implosion for the Fat Man bomb.The idea of using shaped charges as three-dimensional explosive lenses came from James L. Tuck, and was developed by von Neumann.