Reduced Aperture for M16A1. This original A1 issue reduced aperture is legal in the CMP ‘As Issued’ class. One of the two apertures is unchanged, while the other aperture has a 0.042″ reduced bushing inserted. This is the single biggest accuracy improvement you can make for your original rifle.
When looking at the “L”, the aperture is the original size. When not looking at the “L”, the aperture is reduced to 0.042″ diameter. (See photos)