Can an 80% lower be completed with sufficient quality using a hobby/mini milling machine?  Anybody here have any experience with a hobby mill to recommend one?  Getting a 'real' milling machine is pretty much out of the question for me right now, and I'm just wanting to learn.  Is a hobby/mini mill ok for this application?

I would think so as long as it could be mounted solidly. What you're going to run into is finding a high quality table to go with it. Along with runout on the quill, a level, accurate table is super critical.

One of the Rong Fu RF45 machines should do well for you . Its about the biggest yu can get in the relm of the mill/drill. I have one in th shop and it runs like a champ.

I've done one on my LMS Mini-mill. It's ALL about workholding.The big problem you'll run into is the tooling length to cut the deep pocket, but if you know what you're doing, it's not too bad. Certainly doable, but it's about at the limit of my little machine's capabilities, in terms of rigidity - getting a good surface finish (so it looks pretty) takes some concentration.

ETA: What sweptvolume said about the table is very true. Hobby mills are good to start out on if you have some basic skills, and want to hone them. If you start off with some simple projects using soft materials and work your way up, they can be great to learn on. The big problem is that you have to work harder to get pieces mounted well, and to keep the machine true. On a bigger machine, you can focus on other parts of the process, but if you're doing anything of appreciable size on a mini-mill, your setup has to be good. Good machinists can do some amazing things with these small mills (I know of a guy using one to make some VERY nice mechanical watches - gears and all), but it takes a lot of practice and experience to get to that level. An 80% lower is a good intermediate project, but I wouldn't start with it, and I would say there are plenty of other things that you will eventually consider to be 'beyond' the skill level that was necessary to complete it. Its size is the limiting factor - not its complexity.

http://www.homegunsmith.com/cgi-bin/ib3/ikonboard.cgi

A number of people have used a variety of machines to accomplish an AR build. This site has a lot of good information and Good luck!

I have done them from 0% on the HF mini-mill.   Now I have a 20" square column bench-top mill, which is much better.

where are you located in MO ??

Maryland Heights (st.louis area)

I have done a number of AR receivers with one.  It is challenging but not impossible.