My AR-45 project is starting to work. The goal is to build an AR platform rifle chambered in 45ACP, and feeding from a standard AR mag. Wally (of GBC fame) pointed out that this would require an AR-10 based build, instead of an AR-15 based build, and that has made life allot easier.
Here is the prototype magazine. You'll notice the follower is two pieces of sheet metal braised together. Aside from the spring I could build the mag from scratch this way, but but buying a mag body is easier.
And here are the internals of said magazine. The curved piece is the front block to keep the cartridges under the feed lips, and the feed ramp. The other flat piece is the back block to keep the cartridges stacked neatly.
The next step is to build up the lower, and order an upper. Then I can put the barrel assembly together.