As you would expect with any gun that is produced, Armalite tried to provide accessories for you to purchase with your new AR-180.
Taken from this pdf available at Small Arms of the World we see many accessories that were available to outfit your new rifle.
http://www.smallarmsoftheworld.com/search/pdfdmp.cfm?docid=868.pdf
The subject of this article are the steel Sterling Magazines.
http://www.smallarmsoftheworld.com/search/pdfdmp.cfm?docid=865.pdf
These rifles shipped with two 5 round or 20 round aluminum alloy magazines and one of the first things many owners did was buy more. These particular steel magazines had an excellent reputation for reliability and durability. Something many aftermarket magazines did not. I’ve had confirmation from several sources that these were the magazines of choice for those lucky enough to own select fire AR-18’s. The original alloy magazines had a reputation for feed lip problems during sustained full auto. They were also advertised to fit the AR-15 as well and if you own both guns, it made sense to buy these magazines.
Here are some examples I own.
They can be identified by several features, the most notable of which is the base plate. Unlike the original Costa Mesa 30 round steel magazine, the base plates are marked as shown. They also feature a single hole, near the top, on each side.
You will also note that the 20 round magazine is unique in that it curved as well. All original alloy magazines are of the straight design.
Now is my time to speculate a little about the 20 round Sterling magazine.
They are very hard to find and I believe that is because many did not buy them. Put yourself in the mindset of a new AR-180 owner. Your rifle came with two 20 round magazines. If you wanted to buy more, would you order more 20 rounders? I wouldn’t, and I think this is why so few are found today.
This example is the only one I have seen in person and you can see from the picture that the condition is not pristine. It actually looked much worse than this when I got it. Covered in rust. I rubbed it down with some gun oil and steel wool and I was able to knock most of the rust off. I don’t know if I will try to get it any cleaner at this point.
Please comment and let me know if you have any more information about these magazines.