The ones at AR15Plus seem extremely expensive, though they are specialized metals, so that is probably the reason.
If you don't have experience using a drill press and taps, you probably shouldn't start making a receiver. Get a drill press and a few taps and experiment working on aluminum block.
Start here: CNCGUNSMITHING - www.cncguns.com - Home of the AR45
I have found three major methods of doing the build:
- Jig: The jig is somewhat expensive, but this is the most accurate.
- Receiver Template: Clamp a 100% receiver to your 80% and drill, not as accurate as the jig, but does get the job done.
- Paper: Get a paper template and drill through it.
- Eyeball: j/k
- The least expensive 80% I've found is $27.95 each or $24.95 for 3+, referred from CNC Gunsmithing. I actually just purchased 8 of them.
AR15 Lower Receiver 7075-T6 Alloy Forging, Military Spec-D S Arms
- A full list of tools is outlined at CNC Gunsmithing: CNCGUNSMITHING - www.cncguns.com - AR15 80% Tooling / Drill Jig
- You should also get a drill press, forget about doing this with your cordless! HarborFreight has decent prices on starter drill presses.
- Large tap wrench, probably get one from HarborFreight, though I'm not sure what size you need, you'll need this to tap out the buffer hole. Some instructions here on how to make one.
Other links, I have no affiliation with any of these sites.
Patriot Publications | The works of D.A. Hanks
80% receiver FAQ
AR 15 Lower Receiver Complete Kit
Building an AR from an 80% casting
AR15.COM :: Forums :: Building the KT-15 - By Secret Gunsmith - For Reference Only
OSI Gunsmithing Tools
80% Receiver Sources - Survival Monkey Forums
AR-15 Receiver Print
Finally, you shouldn't be selling receivers you make. You are allowed to build them, but manufacturing them for sale is kind of a big no-no to the BATF; remember always be safe, no one wants to wind up in federal-rape-you-in-the-ass-prison. I mentioned that I ordered 8 of them, I want to have enough to practice on; if friends are interested, I'd sell them a blank at cost and help them machine it.