I happened to become a fan of the 7.62x39 AR-15 purely by chance. A couple of years ago I came across a very nice original Colt R6830 for only $900 and immediately bought it, planning to resell it or turn it into an M4. However, after shooting it I was actually quite impressed and decided to keep it as is. Now I have two.
I'm sure Colt gave us a perfected 7.62x39 AR-15 purely to expand their product line and customer base in order to sell more product. I don't think the weapon had any intended military application. The world is full of AK-47s and Browning Hi-Powers when "sterile" weapons are needed for plausible deniability.
The Colt R6830 Sporter Lightweight 7.62x39mm first appeared in the 1993 model year. I have an original Colt New Products brochure from that year featuring it on the center page. Given that the original ad is a photo of a deer in the woods with an image of the rifle overlaid on top of it along with the subtitle "Modern semiautomatic performance for brush country hunters", I'd say Colt's main marketing strategy was to promote it for hunting use. Further in the text they also mention informal target practice, law enforcement, and home security.
[img]http://photos.ar15.com/WS_Content/ImageGallery/IG_LoadImage.asp?iImageUnq=3213[/img]
As for the magazine issues, unfortunately the R6830 appeared to close to the ban for the aftermarket to develop really good magazines for it. Once the ban was in effect and most of the market disappeared, there was little point or incentive for anyone to develop really good, appropriate high capacity magazines. Fortunately, however, there are some decent high capacity magazines available. These are the hybrid type where an AR-15 feed tower is attached to an AK-47 magazine body. These were available from companies like Scherer, G-Tech, and yes, even USA Magazines. Here is a pic representing some of the magazines in my collection:
[img]http://photos.ar15.com/WS_Content/ImageGallery/IG_LoadImage.asp?iImageUnq=3215[/img]
The AR-15 that Colt produced primarilly for export was the R6510, chambered in .222 Remington, for sales in countries that prohibited weapons chambered for cartridges in current military use.