I can't come up with cleaver titles anymore.

More work on the Uzi.  Last time I showed off my overly complicated CNC'd receiver bit.  This time I'm going to start putting it together.  I'm not using a jig, so I'll have to use the parts themselves to keep everything aligned.  The first thing I did was weld some bits into the new receiver.  After some careful hand fitting, I welded in the barrel restrictor ring/feed ramp, rear grip mount(removed from my original receiver chunk), and most importantly the blocking bar.  The blocking bar is necessary for all semi-auto Uzi builds.  It's sole purpose it to prevent a full auto bolt from being installed into the gun, and it must be put in before the receiver is complete.  Even before it's complete, without the blocking bar installed you are in possession of a machine gun receiver in the eyes of the law, so it's best to put it in as early as practical.  Here you can see the parts in place, as well as the weld going down the center where the two machined halves meet and where the rear grip mount welds have been ground down for clearance.

I'm going to be using my barrel to help keep things aligned.  The problem with that is that my original SMG front trunion and semi-auto barrel don't exactly match.  One of the things IMI did when they started exporting a semi-auto version of the Uzi was make the semi-auto trunion smaller in diameter so that a full auto barrel wouldn't fit.  That means that the hole in my FA trunion is .040" bigger than the barrel.  That makes for a sloppy fit and way too much wiggle room for my liking.  I was going to machine a bushing to press in, but then I decided that was way too much work because it had to be so thin.  It occurred to me that shim stock would work great for this.  I used some brass shim and made myself a bushing, carefully filing the ends so that it fits perfect.  Since this is a pistol build and I'm legally allowed to use a short barrel if I want to, I'm not worried about it being removable.  You can also see how this front stub looks practically new.  Even though it came as part of the same parts kit, it definitely didn't come off the same gun as the rest of my parts.

With that set, it was time to put things together.  I had already welded the sling swivel/front grip mount section of the receiver to the front stub using my machining jig to hold things square, so it was time to attach that to the main bit of receiver.  I'm using my barrel for alignment, and here's how everything fits together.  The rear barrel restrictor ring/feed ramp ring aligns the new receiver to the front trunion. The Uzi headspace is determined by the bolt contacting the trunion, so nothing here needs to be ultra precision.  Since the barrel is new, I've got the exposed parts covered in blue tape to keep them from getting scratched.

Now the exciting bit, welding without a jig.  I have to make sure everything stays straight, and I want to get full penetration welds, without burning through the sheetmetal. Enter the copper backer.  Steel won't stick to copper when welding, so you can weld and get full penetration without leaving blobs of weld on the back side.  I didn't actually have any thick copper sheet, and it costs more than I wanted to spend for the little amount that I needed, so I decided to think outside the box and into the home improvement store.  I bought some copper plumbing connectors, and smashed them flat.  Presto, $.49 instant copper plates.  The barrel takes care of our axial alignment between the pieces, but I still had to get the right length so that everything fit together like it was supposed to.  Since the rear grip mount is welded to the new receiver, and the front of the grip locates off the protrusion welded to the front stub, I could use the grip frame it's self to set the length of this section.  I carefully fit the parts so that there was zero gap between them, then I used a variety of vice grips to hold everything in place, backed by my copper plates.

After tack welding and checking to make sure everything was straight and in the right place, I burned in some welds.  With that done, I decided it was time to cut the ejection port in the receiver.  I also dressed the welds some, because I'm impatient.  Here's where we sit at the end of the day, actually starting to look like something.