[marktwain]

M16/A2 shoots a 5.56mm/.223 cartridge:

28
Describe the ranges for the M16/A2 Rifle.

* Maximum Range - 3,600 meters

* Max Effective Range for a Point Target - 550 meters

* Max Effective Range for an Area Target - 800 meters

http://www.armystudyguide.com/content/army_board_study_guide_topics/m16a2/m16a2-study-guide.shtml

[Anoreth]

Thus, the US Coast Guard’s firearm safety rule #4: Know your target and what is beyond it.
An M16 5.56 round goes a long way.