[QUOTE=DirtyLaundry;9547411]Poly lowers are pretty terrible. There is not enough material around the receiver extension/rear takedown pin for the type of material being used. When they fail, they fail here. The BCG cycling into the receiver extension stresses transfers forces to the portion between the receiver extension and the take down pin and they catastrophically fail.
Yeah, but if it breaks you now have and AR pistol!