Men Against Fire: How Many Soldiers Actually Fired Their Weapons at the Enemy During the Vietnam WarIn a squad of 10 men, on average fewer than three ever fired their weapons in combat. Day in, day out — it did not matter how long they had been soldiers, how many months of combat they had seen, or even that the enemy was about to overrun their position. This was what the highly regarded Brigadier General Samuel Lyman Atwood Marshall, better known as S.L.A. Marshall, or 'Slam,' concluded in a series of military journal articles and in his book, Men Against Fire, about America's World War II soldiers. Marshall had been assigned as a military analyst for the U.S. Army in both the Pacific and Europe. The American, he concluded, comes 'from a civilization in which aggression, connected with the taking of life, is prohibited and unacceptable….The fear of aggression has been expressed to him so strongly and absorbed by him so deeply and pervadingly — practically with his mother's milk — that it is part of the normal man's emotional make-up. This is his great handicap when he enters combat. It stays his trigger finger even though he is hardly conscious that it is a restraint upon him.'
Marshall's claims did not go unchallenged, but despite the disagreements they were widely accepted as truth both within the nation's military and by those writing about the war and its American fighting force. Marshall continued in his role as analyst and self-proclaimed military historian before, during and after the Korean War, authoring many more books and frequently appearing as a guest lecturer at Fort Leavenworth and other installations around the United States. It is not an exaggeration to say that he was more or less a living legend by the mid-1960s. Largely due to his influence, noncommissioned officers and officers sent to Vietnam at the beginning of the American buildup were concerned that their soldiers and Marines would not fire at the enemy.
http://www.historynet.com/men-against-fire-how-many-soldiers-actually-fired-their-weapons-at-the-enemy-during-the-vietnam-war.htm/2 I remember hearing that one reason all soldiers were given weapons with a full auto capacity was so that when they did fire, they would put a lot of rounds downrange. When I was in the Air Force we were trained to fire 2 or 3 round bursts from an M-16. It's tricky, but you can do it. Firing in the full auto mode usually resulted in only hitting butterflies after the third round because of muzzle climb.
For the first time in military history, the common rifleman of the infantry would have a fully automatic weapon. Prior to Vietnam, from WWI (possibly WWII) onward, it was common to have one "fully automatic" man assigned to at least a squad (12 men) or platoon (40 men) level. The "fully automatic" infantryman might be armed with a machingun, or more commonly a BAR (Browning Automatic Rifle). The BAR was invented during WWI, and carried in combat in WWII, Korea, and for a time, Vietnam during the early days. The fully automatic M-14 rifle was used and intended to replace the BAR, but was NOT totally satisfactory. Ultimately the M-16 rifle was used and accepted. This rifle (the M-16) gave full automatic acceptability. Now every infantryman had "rock 'n roll" capability, and the old time tradition of assigning a "fully automatic" man to the squad/platoon was NO LONGER necessary.
After Vietnam, the army found out it was wasting ammunition (3,000 rounds used to produce one enemy casualty) so the NEW fully automatic M-16's were converted to shoot only "short bursts" instead of full "rock 'n roll".
http://wiki.answers.com/Q/The_effects_of_technology_in_the_Vietnam_War I have read that many of our soldiers today use the semi-auto mode of shooting more than the burst fire mode.