Special Weapons, LLC makes a rifle they call the "SW5," which is an MP5 rebuild with some American made parts, semi-auto only function and a legal 16" barrel. Prices are floating around $1000 or so, and it is legal everywhere except the obvious CA/NJ and probably CT too.

Did someone say JDM? I have what you are looking for in my collection:

100% JDM Arisaka Type 99, Kokura arsenal. Series 24 if memory serves. World War Two standard issue.

If I get lucky, one of these days I'll find a series 30-35 Toyo Kogyo (Mazda!) assembled Type 99. Kokura arsenal supervised their production, however. Not many people can say they have a rifle and a car produced by the same company.

The only other company I can remember that produced rifles and autos is Daewoo, however both Daewoo cars and rifles are rare in this country.