What is one of the characteristics of the M16A2 rifle?

The M16A2 rifle is notable for its ability to operate in both semi-automatic and burst firing modes. This characteristic allows the shooter to switch between firing one round at a time in semi-automatic mode, or three rounds with a single pull of the trigger when in burst mode. This versatility is significant in combat scenarios, as it gives the operator more control over their firing capabilities based on the tactical situation.

The other options describe features that do not pertain to the M16A2. For instance, the rifle operates using a gas-operated, direct impingement system rather than being manually-operated. Additionally, the M16A2 is chambered for 5.56mm ammunition, not 7.62mm, which is featured in other firearms. Finally, the magazine capacity for the M16A2 is typically 30 rounds, rather than a fixed capacity of 20. Thus, the ability to operate in different firing modes is a defining characteristic of the M16A2, making it an effective weapon for various combat situations.