Re: Building AR's instructional material
Check out the AGI (Amer. Gunsmithing Institute) series of videos. Depending on your working knowledge of AR-type rifles, experience with the platform, etc., you may want to start with the basic like the "AGI AR-15 Technical Manual" video which covers basic function of the AR, general assembly/disassembly, proper maintenace, etc. If you want to get straight into building, then look at the "AGI Building the AR-15" video which covers upper and lower assembly, as well as barrel installation, head-spacing, etc.