RHOOD, sign up for an account at 3D Content Central, that's where all of these files are available from. Some of them I am redrawing to have all the features.
Also found a solid model of the VTAC handguard and assembled that last night:
I know that to many this may not be conciderd building and AR, but this one is a smith upper, stag lower, magpul grip and fore end, leupold MK4 CQT, love that optic, TLR-1 light, Vltor muzzle break. I like him anyway.
Also, the A3 upper from cnc has some issues. Maybe not in solidworks, but when you view the wireframe, you can see triangles (mainly in the FA housing). Rendering engines dont deal with triangles very well.