I built my first AR15 bottom yesterday. I had a pretty good "How To" booklet with pictures. Not difficult at all. There are a lot of little springs which look a lot alike and some pins which are similar. Overall it's pretty simple. The parts for the most part are smaller than an M1 Garand but not difficult, I'd say on a scale of 1-10 with 10 being the most difficult it was about a 4. Next build will be easier. I'll post pictures once I add the upper and butt stock. The upper will either be a .22 or a .308.
Bill