The United States is quietly rewriting the rules of small arms, betting that a radically different rifle and machine gun will decide future firefights. Instead of tweaking the familiar M4 and M249, the Army is fielding a new family of weapons,

It can loiter over targets while sending back video through a two-way data link. It can destroy targets from ranges out to 900 miles. And now, it can adjust course in flight to destroy moving targets … the Tomahawk missile, often the first weapon to ...