Monday, August 12, 2013

How to build your own Uzi from a parts kit. Now a motion picture.

No sooner than I got the last parts in that I needed to finish my Uzi,  than a new kit arrived on my doorstep. This kit is a German/European kit, and is in great shape. It also came with what is known as a "center repair section" from the good folks at Global Machine and Tool. The repair section speeds up the build process by a factor of 10 compared to piecing together a bunch of demilled receiver chunks. You take some measurements, square off your front and rear receiver pieces, weld them on the ends of the repair section, (making sure your blocking bar is welded in as well), and then weld in a couple of small semi-auto pieces like a feed ramp and a stock mounting block, then rivet in an ejector, and you're done.
An inexperienced builder could finish an Uzi in a matter of hours if they used the GM&T repair piece.

Anyway, here's the video. I'm about as much of a film artist as I am a gunsmith, which is to say, not much.

Sunday, August 4, 2013

Modifying the Uzi bolt to semi auto

Continuing one with our Uzi project......
The SMG bolt must be modified in such a way that it can no longer be used as a fully automatic bolt, and can only be used to fire semi automatically. One shot per pull of the trigger, and all that.
This is probably the hardest part of building an Uzi, and requires the use of a milling machine. A drill press and a cutoff wheel could be used, but would also require abundant use of a file to get everything spot on.
Semiautomatic bolts can be purchased, however, in lieu of machining your own. I'm a real tightwad when it comes to stuff like that, and I own a number of machine tools, so I just forgo spending the money on the finished parts, and instead spend my money on screwing up one or two parts before finally lucking out and getting one right, in effect wasting twice the time and money that could have been spent on simply purchasing an off-the-shelf part.

Starting with pics from a previous post, we took our annealed bolts and drilled a hole in the rear of the bolt, all the way through to where the fixed firing pin was. This allows for a floating firing pin to be used.
We also drilled a 1/4" hole in the upper right corner of the bolt. This is to save us a little time on the mill, down the road.

Next, the sear "feet" on the front of the bolt are welded up. This is so the original sear will no longer control movement of the bolt. I laid a ton of weld on these areas, just so I knew that I wouldn't have to go back and add more after machining the welds down flat with surrounding areas. Hence the "gob-welded" look.
On the left, an un-modified bolt, in the middle, a welded bolt, and lastly, a bolt with the welds milled and sanded smooth.

Next, we will be revisiting that hole drilled in the upper right corner of the bolt. This hole is there so we can mill out a slot on the right side of the bolt and the bolt can now clear the blocking bar in the receiver. I milled this out with a 1/4" end mill, then started filing to get it to clear the bar by a few thou.

Here is more of the bolt with appropriate areas filed and sanded flat.

Now, we need to machine a large chunk out of the bottom right side of the bolt, so the semi auto sear has a place to ride. I thought I got a pic of this entire process, but it seems I only got a half-way-through pic.

After a couple of failed attempts to machine the striker (mainly because my milling machine is in pieces at the moment, getting some upgrades), I ordered a striker for the gun.

Since I'm building a carbine, the gun must have a 16" barrel, and have an overall length of 26" with the stock collapsed. In order to facilitate that, I had to make sure my barrel was long enough. I turned my barrel out of a 11" barrel blank, and machined a barrel extension 7.5" long that I welded on to the 11" barrel to make it a permanently-legal carbine barrel. Since I think the Uzi carbines look ridiculous with the "ant-eater snout" barrels, I used a piece of 6061 aluminum tube to make a fake suppressor, so the Uzi wouldn't look quite so dorky.
Here is the finished, raw metal Uzi, with the fake can on it. I intend to do a little machine work on the can to make it resemble a real suppressor, more than it does now.

I'll have pics up in a few weeks of the finished product, and hopefully a range report.

For the purposes of 922r, I have the following parts to replace the original imports.

Receiver -US
Barrel - US
Mounting Blocks (trunnions) - IMPORT
Trigger housing -  IMPORT
Trigger - IMPORT
Disconnector - IMPORT
Buttstock - IMPORT
Forearm/handguard - US
Magazine body - IMPORT
Floorplate - IMPORT
Follower - IMPORT

That brings me to 10 import parts, which means I am legal and ready to go. I'm waiting on the striker and forearm/handguards to arrive.
There was once a letter from the BATFE that the Uzi had an operating rod that was subject to 922r, but they have since changed their opinion and said that the Uzi did not have an op rod, which is altogether correct.

More on this project as I get to it.........

Thursday, August 1, 2013

Converting the Uzi fire control group to semi auto.

Back on the Uzi carbine I'm building........

I ended the last installment of this project with two receiver sections that had been welded together out of four sections. Before I could go much further, I had to weld a blocking bar in place on the receiver, which is shown in the pictures below.
Once the blocking bar was in place and burned in, I took another receiver section from a demilled Uzi receiver I got from Apex gun parts. The receivers they sell aren't good for much, but they do have the necessary center section with the ejection port.
Here is the receiver in one piece. There is still a little grinding and sanding left to do on the welded areas, but for now, it's legally a firearm.

There was a small amount of burn through on the welds that hold the blocking bar in place, these were ground out with a Dremel tool.

Another shot of the quasi-finished receiver.

Now, as with any semi-auto that is built from what was originally a machinegun, you have to modify everything that once enabled the weapon to fire in fully automatic mode. The blocking bar welded in previously keeps a unmodified bolt from being inserted in the weapon, and I have to heavily modify the bolt for it to function in semi auto only.
The next item on the list is the lower, or grip area. A block is welded in place to keep the selector switch from going into the full auto notch. This is just a piece of 1/8" thick scrap metal I burned in and ground down. Nothing special, but it works.
 Here you can see that the selector is in semi auto mode, and is unable to be pushed forward into full auto.

 The selector in semi. You can see that the L shaped link cannot go any farther forward as it is blocked by the welded in metal.

Next, I put the trigger group back in.
Before I put the group back in, I ground the right hand side sear off, so it would no longer control the bolt movement. When I modified the bolts to semi (More on that in another post), I welded up the old sear trip areas, so even IF an unmodified lower were put in the gun (which it can't, more on that in a second), it would be useless as there are no sear surfaces left on the bolt.
 If you look closely, you can see the sear tab on the right side is missing altogether. The left sear tab remains, as that is how the striker will be controlled.

After these modifications were complete, I narrowed the notch at the front of the lower, and welded up the slot in the receiver to match. This way, the slot that the lower's front tab rests in cannot accept a full auto, unmodified lower. It can only accept my highly modified lower.
To top this off, I will also weld up the hole in the receiver where the right side sear hole is. This should show anyone who is paying attention that I have no intentions of ever converting this gun to fire fully automatic.

Next up is the bolt modifications and striker, but that will be the topic of another post.

I hope this, and all of my other building posts, are educational and fun, and inspire some of you out there to build your own legal Uzi carbine or pistol.