Help me understand the law here.

Several months ago I built an AR-15, buying a lower receiver and then mail ordering the rest of the gun.  No problem.

In the Guns-N-Stuff catalog they are advertising metric pattern Austrian STG58 kits for $349.  These kits have all parts except the upper receiver, overall excellent condition with matching serial numbers.  In the ad is a statement "For replacement parts only."

When I saw this I thought of getting one of these kits and picking up a receiver via a local FFL.  However, as I've asked around it seems that doing this is verboten.  How is building an FAL different from building my AR-15?

Or is this a government thing that isn't supposed to make sense?

An often debated topic.   See www.falfiles.com/forums/showthread.php?s=&threadid=71555

My opinion, build away.   It is a step up difficulty-wise from the AR, especially if you purchased your AR upper already assmebled.  You'll also likely need to purchase some specialized tools.

Rocko

The whole "replacement parts only" doesn't apply to you unless you are an importer.  If you are, stick with the AR.

The FAL is more difficult, but not terribly so.  You'll also need some US parts to be compliant.

AR-15 are us made FN's are not here is a link that might help with 922R & 925R
http://www.fnfal.com/falfiles/usaparts.html