The .308 AP4 Barrel Assembly has a Mlitary AP4 light contour barrel with M203 mount cut out.

Thick walled receiver extruded from 7129-T5 Aluminum
16" Chrome-moly steel AP4 contour barrel
308 Panther Flash Hider
A3 Lo-Rider Upper
7.25" Aluminum free float tube
.308 Win/7.62 NATO
8620 steel bolt carrier, heat treated and plated per Mil Spec
Shell deflector and forward assist machined as one unit
Standard A2 front sight assembly