This is a great question and something I've pondered from time to time. I was in the Army from 1967-1970, and for the first 2 years, I was in Armored Cavalry units and the M14 was my assigned weapon. I qualified Expert with it and truly loved that rifle.
In March of 1969, I was sent to the 9th Infantry Division which was headquartered in Dong Tam in the Mekong Delta, South Vietnam. I was then issued the M16 and had to qualify with that. From the outset, I didn't care for it, it seemed like a toy and I was now in the big game where it really mattered.
At the time, the ARVN's were carrying U.S. WWII weapons; the M1, M1 carbines, BARs, Browning 30 cal. machine guns, etc. Since I was a little kid, I had a romantic fascination with the BAR, probably from watching war movies while growing up, and traded an ARVN for a BAR. What a fantastic weapon! It seemed like you could hit almost anything you could see. The only problem was, we rarely ever encountered gooks out in the open where a long range weapon would have an advantage. When we came under fire, it was from the few scattered tree-lines or other concealed positions.
The usual response was not carefully aimed fire, it was lay down a base of fire with everything you had as quickly as you could and call for arty or an air strike. The unit could expend it's entire ammo load in mere minutes and when we were resupplied with ammo, they didn't bring out any of that 30-06 sh[i][/i]it for me, just the standard fare for M16's and M60's. I was now unarmed and carrying the dead weight of that BAR. I carried that sucker in the field twice and gave it up.
It was back to the M16 for me with one bandolier of magazines on my waist and usually one or two more bandoliers in my pack. That's what I carried until the end of my tour. I never developed any strong affection for the M16, but it was the right weapon under the circumstances even if it's not the best battle rifle in our arsenal. What it comes down to is battlefield conditions. In the heat and wet where I was, the difference in the weight of the ammo alone made the M16 the best choice. A better rifle in the wrong circumstances is not an asset, it's a liability.
