The M2 Browning .50-caliber machine gun has been a favorite heavy infantry weapon since the end of World War I. That the weapon has remained in the U.S. arsenal for so long is a testament to its power and flexibility. And no wonder - it was designed by the legendary John Browning himself.  Although the M2 has come in many variants over the years, it has still proven an effective weapon from the last days of World War l, into World War II, the Korean War, Vietnam, the Gulf War, and into...