For the most part the M16 became a reliable rifle once its early teething problems were resolved. It was easy to shoot and developed a reputation for good accuracy. At ranges a hundred to two hundred yards, it developed a good reputation as a man stopper although its killing and stopping power fell off rapidly to the M-14's .308 full powered ammunition at longer ranges. One of its major drawbacks was its small high speed bullet was easily deflected by jungle foliage and other obstacles and penetration was not equal to an AK-47 and well behind that of a .308.

Modern small arms bullets now use a spitzer or sharp pointed bullet. Military ammunition because of humane reasons imposed by the Geneva convention cannot be of soft-nosed or hollow point design. A spitzer bullet becomes unstable once it hits anything solid since the front of the bullet is a lot narrower than its base. Ultimately the bullet will turn 90 degrees and travel sideways, a phenomenon that can be proven by dropping a spitzer bullet on the floor. This is called yawing. The only thing stopping it from yawing in mid flight is the rifling of the bore inducing it to spin, which forces the bullet to travel with its point toward the target.

During the Vietnam era, M-16 rifle barrels were bored with a slow twist to their rifling. A lightweight 55 grain .223 bullet driven at high speed from a barrel imparting a slow twist to the bullet causes the bullet to be inherently unstable which is both a good and a bad thing. Although the bullet spins fast enough in flight to be accurate at close to medium range, once it hits anything, it starts yawing. Which is why the .223 developed such a horrific reputation for tearing huge chunks out of the human body at close to medium range since it starts to upset after penetrating just several inches of tissue, bones and vital organs.