Since I assume the result would be a semi-auto (no way in the U.S. for a non-licensee to make or have made a full auto legally today), you might check out the articles in Shotgun News on things like that. IIRC, one involves using a parts kit to make a semi-auto STEN, a gun a good bit like the K-Gun.
BTW, a gunsmith won't do; you need to contact a licensed manufacturer. You can make a gun (except a machinegun) for your own use without a license, but if you involve someone to make one for you (even an ordinary rifle or shotgun) he needs a manufacturers' license.
Jim
