There are many reasons for keeping the M16 family in service however there is one main reason for keeping it, consistency. For the decades in has been in service it has proven to be one of the most consistent weapons on the battlefield. In fact the M16 family is often compared to another rifle that has also been in service for decades, the AK47 family, which is also very consistent. Another reason for not replacing the M16 family is due to how much in use it is. Over 90% of weapons in the U.S. military is a member of the M16 family. I bring this fact up due the cost of replacing the M16 family of weapons. The U.S. has around 7,000,000-8,000,000 M16s in service with the M16 costing only around $700 to make while a possible replacement, the M27 IAR, costing around $1300 to make. In total, to replace the M16 with the M27 it would cost around 9.1 billion usd. As far as I know, the budget for rifle expenses do not reach that far.

In total, the M16 should not be replaced due to the consistency, cost to produce, cost to replace, and overall popularity and use