More legal requirements and stuff

Since my Uzi build started with a machine gun parts kit, the fire control group has some naughty bits in it that are definitely not legal for use.  We'll need to modify the lower grip assembly so that it's both legal, and usable with the striker fired semi-auto bolt.  The first thing to do is to make sure that the selector lever can't slide far enough forward into the full auto position.  That's pretty easy to do, all you need to do is weld a blocking plate into the grip assembly to limit the selector lever's travel.  I made mine out of some 1/8" steel plate and welded it in.  You can see here the plate welded in so that the selector lever can't go any further forward.

Next up is the sear.  Aside from the FA sear being a naughty bit, it won't work with the striker setup anyway.  It's not shaped right to catch the striker.  There are semi-auto sears available, but I'm cheap and it's very easy to modify the original.  Using a cutoff wheel in my Dremel, I started cutting away at the sear.  The left ear is the only one that matters because it's the one that catches the striker, but I trimmed them both, for good measure.  Here it is with the first ear trimmed:

And with the second ear trimmed:

I eyeballed the angle based on pictures of the commercially available sears.  It's not ultra critical on these things, as long as it's close enough so that the striker can't slip past the sear.  You can see here on the right side of the pic how the modified sear catches on the striker:

I wanted to check my sear engagement on the striker, so I got out my handy Sharpie and colored the sear ears.  Then after assembling things and dry firing it several times, I pulled it back apart to check the wear pattern.  Here's how much actual contact I'm getting between the sear and striker(on the left ear).  Not a lot, but enough.  More contact will lead to trigger creep, and after everything is together and working, I'll see what I can do to improve trigger feel.

That should about cover it

In my last post I mentioned the top cover of the Uzi.  Like many of the other parts, it needs to be modified for semi-auto use too.  It's got this nifty ratchet mechanism on the charging handle to hold the bolt open.  An added safety precaution on an open bolt machine gun, and just a handy feature to have on a closed bolt semi-auto.  The problem is that the semi bolt doesn't move back as far as the FA bolt, so the original charging handle ratchet can't go back far enough to unlock and slide back forwards.  The ratchet unlocking mechanism is super simple, and activates when the spring inside hits the back of the slot.  A lot of people simply take the ratchet mechanism out for their conversions, but I like it.  All that's needed to modify it for semi-auto use is to make the slot shorter to match the shorter travel of the bolt.  Conveniently, the top cover sheetmetal is the same thickness as the receiver, so I cut a leftover piece of receiver to fit the slot.  For my conversion, I needed to add a piece .825" long.  Your results may vary, but it should be around there someplace.

Uzi build, part??

I finally got the receiver of my Uzi finished.  The biggest part left was welding on the rear most section.  Conveniently, the top cover works as the perfect gauge to set the overall length.  Using the top cover as a guide (and taking weld shrinkage into account), once it was tacked in place I clamped my copper plates inside and welded away.  Here's what I ended up with:

The last little bit left was to rivet the ejector in.  I actually bought the proper rivet and used a few of the rivet bucks I made for my AK build to set it.

Apparently, I tried too hard when I set the rivet, because the base of the ejector cracked.  Oops...  It fits into the receiver snug and it's good and tight so I think it will still work.  If it ever does start to work loose, I'll get a new one.