I've done a few 80% AR lowers and want to try my hand at building something else.  How difficult is building a semi auto Uzi from a parts kit and an 80% receiver flat?   I see Atlantic has some uzi parts kits in stock. It's just a hobby so I don't mind spending some money on tools and/or learning some new skills like welding.  Thanks, ARF!

From a flat it is difficult. You need some good strong molds and a very good press. The round front sections cause problems to bend.
If you buy a pre-bent (folded) receiver section it is an FFL item.

Semi bolts are difficult to find and costly if you find one. To convert a FA bolt to semi is some difficult machining on some very hard steel.

From a cut up parts kit it is much easier if you are a good welder.  This is one of the best cut up receivers out there. Cheaper are available but more problems welding.

Check out   http://www.danddsales.com/3.SpecialSales_parts3.html

Have fun and good luck.

I've looked into doing the same. I've found tutorials online about converting the bolt from open-bolt to closed bolt, neutering the fire control group to semi only, and grafting a front trunnion section to an 80% receiver. The bolt conversion looks like the most daunting aspect, but it's not impossible, just a lengthy process. Unless you're tooled up to do all the machining, I'd just buy a semi-auto closed bolt. The receiver-trunnion grafting will require some decent welding skills.

When it comes to building guns from parts kits, it's gonna cost about the same as purchasing one that was manufactured by someone like Century or Vector. But the knowledge gained by solving all sorts of problems during the build is invaluable. If you're up for the challenge and sense of accomplishment, go for it. Careful though, this gun building stuff can get addicting. I plan to build an UZI one day, but first I need to finish a CZ-26, Sterling, and SIG STGW-57 (this one will probably take forever).

Turns out my state's laws won't allow me to build one

I bought a nodak complete receiver and McCay complete bolt and had a buddy weld in the blocking bar. everything else is cake.