M16 A1
 

I hope that I am posting this on the correct forum. I just had a friend call me about the following rifle he saw for sale in the Sportsman's Guide.
With your order, you get a complete M16A1 Parts Kit, everything but the receiver. The Kit has a new U.S.-manufactured barrel, Vietnam-era production and triangle-style forend. Forward assist. Comes with one magazine. Does not include trigger disconnect.

He is wondering where to buy a receiver and also what the trigger disconnect is for. I am just guessing that it is sold without a receiver so no FFL is necessary and also maybe the trigger dis connect is for full auto. Thanks for any knowledge and info!