AR 15 Chambers

Along with using different ammunition, the civilian AR 15 and the military version, the M16, also have different chambers to account for the differences in pressure and velocity. While they are quiet similar, the two chambers still have different names.

The M16’s chamber is commonly referred to as a “5.56 NATO” chamber, which refers to the name of the ammunition this rifle uses. These chambers are equipped to handle higher pressures and velocities and can handle the 5.56 rounds.

The civilian or commercial AR 15 has a chamber not equipped to deal with the heavy duty 5.56 ammo, and for this reason it uses .223 ammo. The chamber of the AR 15 is often labeled “.223 Remington.”