What caliber of ammunition does the M249 use?

The M249, also known as the Squad Automatic Weapon (SAW), is designed to utilize 5.56mm NATO ammunition. This caliber is ideal for the M249 because it offers a balance of lightweight portability and effective performance for infantry support. The 5.56mm cartridge allows the M249 to fire at a relatively high rate of fire while minimizing the recoil, enabling better control and accuracy during sustained fire.

Additionally, the use of 5.56mm ammunition allows for interoperability with other firearms in the U.S. military that use the same caliber, such as the M16 and M4 rifles. This shared ammunition type enhances logistical efficiency by simplifying supply chains and ensuring that units can share resources effectively under combat conditions.