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.

Spoiler Alert!

This post is going to have a lot of words and few pictures, I'll try not to write a novel, but no promises.  I'm a bit disappointed that I didn't take pictures of this process because it worked really well. 

Originally I bought an Uzi receiver flat with the intention of making a bending jig like I did with the AK.  But after reading up on it, it's not a straight square bend like the AK, the nose section of the receiver has to wrap into a tube.  I wanted to reuse my original front end and Hebrew marked rear section anyway and I decided it would be a shame to cut apart a $70 receiver flat just for the bits I needed.  So I decided to do it the hard way.

Spoiler Alert!  I have a CNC mill.  It is not big, and it is not fast, but it gets the job done.  It's a Seig X2D that I converted to CNC myself.  Maybe some day I'll give it it's own build thread.

I decided to make my receiver section on the CNC.  Why?  Because I have way too much time on my hands, apparently.  It seemed like a good idea at the time.  More important than why is how? How do you make a .070" thick sheetmetal part on a CNC mill?  Milling it from a solid block of steel would be way harder than it sounds because as the walls get thin the part looses rigidity and the side walls want to get either pushed away from or pulled into the cutter, making a vibrating mess with no chance of holding a tolerance.  So that method is out.

I decided to think more outside the box.  And into the tube.  I got some 2"x2"x3/16" wall steel tubing.  I'm using A500 grade tubing, which is about equivalent to 1020 carbon steel.  It might seem like it would be too weak for a receiver, but it's stronger than the 1010 steel used in the commercially available receivers(and flats like the one I bought).  Like the AK, the sheetmetal of an Uzi receiver doesn't see much load, so all it really has to do is hold the parts in.

So, how did I make 2" square, 3/16" heavy wall tubing into a 1.6" wide, thin sheetmetal piece?  I cheated, obviously.  This is the bit I'm kinda proud of, and I'm sorry I don't have any pictures of it.  After drawing up a CAD file based on measurements of my receiver pieces and available blueprints, what I did was machine the the sides of the receiver into the sides of the tubing, cut the middle out, weld the halves together, then machine the bottom.  In the pic of my mill above, I'm just finishing up the finish facing pass to get the bottom thickness set.  My welding jig to put the halves together was just a bar of aluminum cut to the right size, and it also served as a backer to support the thin sheetmetal sections so they wouldn't collapse in the vice for the last milling operation.  I elected not to cut the ejection port until later too so that the piece had a bit more stability while milling.  The holes for the blocking bar welds are sloppy as heck because I forgot them in the program and just used my mill as a drill press and I suck at hand drilling holes.  I'm not too concerned, they get welded over anyway.  Here's what I ended up with, one CNC made sheetmetal receiver section.

The Hebrew Heater

As is apt to happen, I sometimes drop off the face of the earth for very long periods of time.  Lots of things between where I left off and now, but I'll spare you the details.  What's important is that it's the middle of hecking winter and I have another wholly impractical project to work on.

Yeah.  The Hebrew Heater, ready to dispense some Jewish Justice.  The Uzi.  Why the Jewish jokes?  Because despite being the star of every 80's action movie and the Secret Service's sidearm of choice, the Uzi was actually designed way back in 1950 by Jews, for Jews, and manufactured by Israeli Military Industries(IMI) from 1950-present.  Like the AK, it's one of the world's most recognizable guns, and millions have been produced(so many that even my well used one is serial numbered in the 9 millions).  The Uzi been used by military or police units in over 90 countries, including this one.

There are a few varieties of Uzi parts kits on the market, original Israeli kits, and, in an historical irony, German kits.  The German military bought this Jewish weapon for over 25 years.  I decided I wanted the original, a genuine IMI built, Israeli used Uzi.  Like all machine gun parts kits, the receiver on my kit is torched to BATF specifications, and there are large chunks of the receiver missing.  Technically, it's now a pile of scrap metal, and no longer a machine gun.  Both the receiver markings and the safety selector markings are in Hebrew.

I'm rebuilding this parts kit as a legal, semi-auto pistol.  Why a pistol?  A couple reasons.  First pistols don't need to worry about 922r(which you may remember was a big deal with the AK, and I'm going to keep track or parts count anyway).  Second, by using a 16" barrel, I can convert it to a carbine with a shoulder stock, as is becoming popular with many off the shelf Glock pistols these days.  There are several Glock to carbine conversion kits on the market.  If it were built as a rifle, it could NEVER be made into a pistol.  Legally you can go one way, but not the other.

There are tens of thousands of semi-auto Uzi's here in the US already, so I could just buy one, but where's the fun in that?  To get this former machine gun together and be legal, I am going to convert the original open bolt system to a closed bolt, striker fired semi-auto.  When it comes down to it, Uzi's are dirt simple, and I've got some special, and overly complicated plans for this project. 

One last little bit of business.  In order to make it clear that I have no intention of using this as a machine gun, one of the very first things I did when I got my parts kit was grind off the firing pin from the original Uzi bolt.  It CAN NOT be used in a functional gun anymore.