Spc. Kenneth Bull of the 25th Infantry Division fires his rifle from the back of a truck during convoy live-fire training at Schofield Barracks, Hawaii, December 2003.

2. M16
Type: Semi or Fully Automatic Assault Rifle
Country of Origin: United States
Caliber: 5.56 x 45 mm (.223 inch)
Cartridge Capacity: 20-30 rounds
Muzzle Velocity: Approximately 3,281 feet per second
Rate of Fire: 700-950 rounds per minute

Although it took a little time to work out the gun's jamming problems during its combat trials in the early 1960s, the M16 has proven to be an outstanding performer with superb accuracy, handling, service length and combat effectiveness. The rifle fulfilled the U.S. military's desire to develop a lightweight modern assault rifle that could replace the semiautomatic M1 and its selective-fire counterpart, the M14. Its innovative features include lighter metal alloy and plastic construction, a simple gas reload system and the use of 5.56 mm ammunition, allowing soldiers to carry twice the amount of ammunition for the same weight of 7.62 mm rounds.

VIDEO: See the M16 in action. 
PUZZLES: Put together these combat rifle puzzles.