If you are making a known design, registering it is a snap. When you make a frame, you have to submit detailed pictures of the frame including the insides. If you are modifying the design significantly, you may be required to submit the actual frame for inspection, and the last time inquired about that the time frame was 1-3 years. If the changes are merely cosmetic, it can be approved within a week or 2. The other thing is most machine shops aren't equipped to do frames from scratch. The wrinkle is the magwell. AR magwells are broached when mass produced. It takes about 30 seconds. To get the sharp corners in a magwell for an ar mag, they have to be EDM'd or wire cut. To get one wire cut, you are looking at about $100, just for the mag well. Bottom line, is that for most machinists it just isn't worth the trouble. To have one custom done, you would probably be looking at $400 not anodized. That is just for the machining. If they have never done one before, they will need to make at least one fixture, and buy the buffer tube tap. I doubt very much you will find someone willing to do that kind of job. We did ours for something to do (and AR 10's were pretty much unobtainable at that time) but for what you can buy them for now, it just isn't worth it