I built mine. CMMG lower, RRA lower parts kit, RRA two-stage NM trigger, Hogue grip, Prince50 mag lock kit. The lower took me about an hour, maybe a little longer, to assemble using directions on AR15.com. I topped it off with a Bushmaster Varminter upper and its a SHOOTER!! I've only shot it about 20 times, but its a true 1/2" rifle, I love it. Total cost was about $1200.