The curved areas came out great. Since it's a 3-axis machine, it's the vertical cuts that have problems. Those I'll have to go back and rebuild with some Bondo. It's annoying, but it still beats the heck out of building a prop like this out of pepakura.
The material I'm using is Medium Density Fiberboard, which can be had at any home improvement store. It's easy on the machine, but I have to reinforce it with something in order to keep it from falling apart once I start doing the detail work and finishing.
To that end, here's the rifle coated in epoxy:
Once that sets up, it'll make a nice composite surface that I can sand, file, cut, and drill without losing details I want to keep.
Here's the carrying handle and rear sight:
This evening I had Lopez carve out the drum magazine:
An old college classmate of mine who's into all things AR-15 is going to be getting me some NATO 5.56x45mm dummy rounds so I can use them for the visible round details in the magazine. I'm also going to have to source some acrylic tubing to serve as the outer shell, but that should be easy enough.