The Korean War showed a smaller, lighter round fired from a lighter rifle was the future.
Here's What You Need to Remember: The obvious advantages of the M16 over the larger, heavier M14 in Vietnam, as well as the large number of U.S. troops deployed to Southeast Asia, led to further purchases and eventually the M16 overtook the M14 completely.
The M16 rifle is one of the most iconic weapons of the post-World War II era. American fighting men have carried the M16 in one form or another into combat for more than fifty years, from Vietnam to the present day. The story of the original M16, whose descendants the M16A4 and M4 carbine today fight in Syria and Iraq against the Islamic State, goes all the way back to the 1950s and the institutional soul-searching that came after another war—Korea.