Here's one of my GBBR's, my Western Arms M4
It's set up like what a standard army M4 might look like, 4x32 ACOG, KAC type 600M back up sight, PEQ-15 with Laser & Light, 14.5" outer barrel and I'm using it with Co2 Mags
I'll put up some pics of my other GBBR M4 build next week