Those who manage the weapons acquisition process are often frustrated by barriers to change posed by military services, which generally prefer buying weapons that perform traditional missions in traditional ways. This essay explores the way in which large organizations adapt to innovation by focusing on the U.S. Army's purchase of the M16 rifle. Because the M16 represented a break with the Army's rifle tradition, the service resisted Defense Secretary Robert McNamara's efforts to introduce it in 1962. Yet by 1966 the Army standardized the piece, replacing the very traditional M14 rifle in the process. The essay concludes that this adaptation is best explained by the existence of a declining Army-wide consensus concerning the Army's rifle tradition. Although policy remained traditional, many in the service were unhappy with the M14. McNamara's initial efforts and the M16's performance in Vietnam convinced others of the rifle's utility, and this freed the organization from its attachment to tradition.