To legally build a semi-auto Uzi, you need to run a closed bolt system vs. the original open bolt. Now the open bolt design was the picture of simplicity albeit with a pretty big bolt. The closed bolt system uses a striker, and while a little more complex, it has a lot of moving surfaces that are parkerized. This means they are relatively rough and need to wear in plus they need serious lubrication during this period.
My experience with my Uzi was that oil alone didn’t cut it. Once I moved to using a 1″ chip brush and applying a light layer of Super Lube all over the bolt, striker and insides of the receiver and top cover, the reliability sky rocketed. At this point, it has worn in fairly well and the action cycles very easily.
My recommendation to anyone building a semi-auto Uzi is to use Super Lube Multi-Purpose grease both during break in and for ongoing lubrication of the bolt and striker system. I use regular oil on the fire control group.
I hope this helps you out. It made a world of difference with my Uzi.
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I built an Uzi a few months back and had trouble with it firing. A challenge a person has in the firearms industry is finding time to enjoy shooting! At any rate, I took it out the first time and had really light primer strikes with the firing pin – I’m talking you could barely see there was contact. So with the Uzi refusing to go bang, I had to do some digging.
I got into Uzis because of all the movies and TV shows in the 1980s. I decided to finally make one during the Winter of 2017/2018 and chronicled my efforts. The first time to the range resulted in a lot of good natured ribbing from my brother-in-laws as we could not get it to fire. We could hear the striker hitting real hard but no bang. Luckily I had other guns for us to shoot so I put the Uzi back in the bag and took it home where it then sat for a couple of months.
I did some digging and process of elimination and got it down to a few possibilities that in some cases I had already addressed. The following is my journey and what I did to sort matters out.
The Uzi closed bolt system is a huge chunk of metal and moving parts. When brand new, these parts still have their porous surface finishes on them, rough spots from machining and what not. You need to make sure everything is lubricated. Remember the old saying of it slides, use grease. If it rotates, use oil. I used Tetra gun grease on all sliding parts. I definitely wanted the big bolt body to slide easily. I also did put a light coat of Mobil 1 Full Synthetic 10W30 on the firing pin but really nothing rotates in there. In the trigger group, I used the oil also on all pivot points.
For me, I heard the need for this when I assembled the carbine for the first time. There was a very dry slow-moving sound and grating feel when I first ran the action during assembly. After lubrication it made a world of difference. I could feel and hear the striker hitting far harder. The important point is to lube your weapon. This definitely helped but it did not solve my problem in this case but I could tell it would definitely impact the operation of an Uzi.
Note: When I wrote this I was using Tetra Grease but I am now using Super Lube and it works fantastic on my Uzi. Click here for the write up.
Top Cover Bent
To be honest, I thought for sure this was going to be my problem after a fellow at McKay suggested I check it. I always thought the cover seated hard and I could not release the latch without a tool. As soon as the fellow suggested it I put one and one together – I bet it warped when the third party welded on the Picatinny rail section.
So, I did some digging on the web to figure out what to do. It turns out that you should be able to insert a 0.005″ feeler gauge between the bolt and the cover at the ejection port. Guess what? It wouldn’t go in – the first rib was tight and the far rib was impassable.
Before I go further – one quick comment on feeler gauges. Not all are equal. I have a few in my toolbox but the one I use the most is is this ABN unit shown aboe. It is accurate enough and it has a ton of gauges. I point this out because not all of these gauge sets are complete. For example, several of my gauge sets jump as the manufacturer just included the blades needed for their equipment. I’d recommend getting a set with a lot of SAE and metric blades so you have flexibility. For the Uzi dust cover, you need the 0.005 and 0.015 gauges.
Next was to take some plywood stock I had lying around and make a jig. Basically you want two pieces of wood (any wood to avoid marring) that are the same height. The top cover will be suspended between them so you can adjust the cover either up or down.
I then made two little punches. One is made by gluing and brad nailing two pieces of 1/2″ plywood together so I could hit both ribs of the top cover at once. I also made a punch out of a single piece of plywood to adjust just one rib. I then got out one BFH (big frickin’ hammer) to whack with.
If there’s one thing I have learned – don’t go crazy hitting stuff. I put the jig right on the floor for good support and then the dust cover on it. Note that on the front part, I pushed the wood block back until it was supporting a thicker part and not just the thin neck.
So, I gave it a tap – not a very hard one with the thick piece on both ribs and took it over to test. It sure went on the receiver easier. Wow – it overshot the mark. I could now very easily insert the 0.015″ feeler gauge too. My understanding is that you don’t want it that loose or you risk the bolt jumping the sear and resulting in an uncontrolled mag dump. No joke – I don’t need that in my life ever.
I took the cover off the Uzi and flipped it with top now facing up and I tapped down even lighter. It really is surprising how easy the dust cover bends. I thought given the thickness of the sheet metal and the two ribs it would be much stronger but no.
I then took it back and installed it on the Uzi. It was starting to fit better. I definitely noticed that the ribs were different in terms of their gap so I switched to the smaller 1/2″ plywood punch and focused on one rib at a time. Tap and test, tap and test. If I went too far one way, I would flip the cover and tap it the other way.
After about 15 minutes I had it dialed in. The 0.005″ gauge would slide in and the 0.015 gauge met just a bit of resistance.
In working the action you could both feel and see the improvement. As always, there was a nice firm thud of the striker. Problem solved? No – it wasn’t. Argh. It was a definite improvement in operation but did not solve the problem.
The Uzi Bolt Blocking Latch
The web is a wonderful thing. I continued to surf around and read more about peoples’ experiences with Uzis not firing. Finally I read one that caught my eye – the striker has a particular orientation that must be followed to clear the bolt blocking latch. Wow. I knew I didn’t know about that when I installed it because the light strikes definitely indicated the striker wasn’t reaching the primer and this would explain a lot.
Okay, #31 in the above diagram is the bolt blocking latch and #30 is the spring. The bolt blocking latch’s purpose is to reduce (not eliminate) the chance of an out of battery firing. It does this by blocking the striker’s base. In normal operation, it is depressed and the notch in the base clears the latch as it travels forward to touch off the primer. Now there are three key things here and I’ll tell you what I messed up.
The spring must be installed correctly.
The latch must move freely
The striker must be rotated such that the notch is in the right place- you can install it 180 degrees opposite.
So, your’s truly bombed the last one. I did not realize there was an orientation issue. The model B striker’s base is a half circle. The notch must be at the bottom to clear the latch. In this next photo, you can see I have it installed backward:
The following photo shows the installed Uzi bolt blocking latch. See how the bottom part sticks out? That is what will need to clear the notch when it is depressed during normal operation.
Note, I was working on a full size Uzi with a McKay semi-auto receiver and bolt group. Your bolt group may look a bit different.
When installed correctly, the striker sits in its seat and the seat sits in the striker guide like so:
You can see in the above photo how my latch was chewing on the improperly installed striker. As a visual reference for the correct orientation, see how the striker’s base is facing the part of the guide that has a depression in it. When installed, it will look like this:
You can see an immediate difference because when you depress the latch, the striker can fully travel forward and sticks out of the bolt face ever so slightly. That’s what we want!
Verdict – problem solved and fun was had at the range yesterday. The Uzi is still wearing in and smoothing out. We put about 100 rounds of 124 grain S&B FMJ through it.
The carbine was accurate and a lot of fun. I am going to find a bit bigger optic for it – probably the Vortex Crossfire like I am running on my POF-5.
Regardless, I hope this helps you out!
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So the semi-auto 9mm Uzi carbine build has the Molyresin applied and is ready to go together. The following is an overview of the final assembly steps:
1] Install the grip frame assembly. Insert the tip first and swing the back up into position. Install the grip frame takedown pin. If the assembly will not go into position you may need to remove the bolt safety. The McKay receiver and bolt do not use that part. If you have questions about the grip assembly and preparing it for semi-auto use, click here.
2] Install the stock bracket with its 1/4″ screw and then the stock itself with its three screws taking care to use the correct bit on the slotted screws. Make sure the bolt doesn’t stick in too far. If you have questions about converting the quick detach stock to be permanently attached, click here.
4] I installed the barrel nut catch and spring plus the front sight. Slide the catch far enough back that it hooks the receiver and does not come back out.
5] I then installed the rear top cover catch and rear sight. The trick here is to push down on the flip sight while pushing the screw through so the threads can engage on the other side. The little tiny but just locks it in place – the receiver itself is threaded also. Note, I did have an issue with either the thread on the bolt or the receiver. I could not get the rear sight screw to enter on the opposite threaded side. After playing with it for a few minutes it dawned on me that either the screw or the threading in the “ear” of the receiver could be messed up so I installed the screw from the opposite direction just to chase the threads real quick and that solved whatever the problem was because when I then tried to insert it the correct way, the screw went right in.
6] Rather than mess with rivets, I tapped the front sling for a #10-28 screw. I sanded down the head of the screw to avoid interference with the bolt and then applied medium Loctite to the thread when i installed it. If you need to remove more of the screw head later it can be readily reached with a Dremel and a flap sander or whatever bit you wish.
7] The 16″ semi-auto barrel slide right into the front trunnion and into the ring of the semi-auto feed ramp. Rather than use the barrel nut, I opted for a very cool two piece barrel shroud from Title II Arms. It is solid aluminum and exceptionally well made. Note, I show a light on a rail adapter on the bayonet lug. It looks cool but I actually removed it as my hand’s natural hold runs right into it. It’s not a reflection of the CAA rail but it’s just not for me. With it gone, my hand can go right out to the end of the handguard and is much more comfortable.
8] Next it was time to sort out the striker fired bolt system. This raises a critical legal point –the weapon must fire from a closed bolt. This means you can’t use the original open bolt. After some digging, I decided to use the McKay closed semi-auto bolt system for my build. Now McKay components are popular and they were out of stock on the complete bolt assembly but Robert RTG had it in stock so I bought it and other parts from them. As of my writing this, for example, McKay has their receivers in stock, bolt assembly but not the barrel so you can check between both firms plus McKay says they sell to Sarco and Apex.
9] I had to do some reading to figure out how the bolt went together as I had never seen anything quite like it before. The best write-up I could find that really helped me is right here. In a nut shell, take your original bolt, push out the extractor retaining pin and then push the extractor straight out the front of the bolt. From the rear, the extractor looks like a screw due to the slotted head but it is not. The slot is there to make it easy for you to rotate the extractor into position. Insert the extractor into the new semi-auto bolt. You will notice that with your semi-auto bolt a small blocking latch and pin are included just like you would see in the Uzi Pro Pistol – indeed, the whole bolt assembly is very similar to the Uzi Pro Pistol if you look it up. The little spring and the latch are inserted into the bolt and held in place by the extractor pin in the semi-auto bolt.
Ok – this next photo shows a problem that I didn’t find out until the first trip to the range. At the lower right of bolt is a pin that holds the extractor in place plus you can see a tab sticking down – that is the locking latch. Now look at the striker. You can’t see clearly but it is a half moon shape and I have it installed backward. The notch, or part of the striker’s base that is missing should be what goes against the bolt blocking latch. If you get it backward the weapon will not fire and you’ll notice the striker base getting beaten up by the latch.
Here’s the blocking latch – see how the bottom part stocks out? That is what will need to clear the notch when it is depressed during normal operation.
Here’s what it should look like – note how the striker bar has a smooth side and one with a relieved/depressed surface? The notched striker base goes towards the smooth portion:
Here you can see the base that is towards the relieved/depressed area plus you can see the blocking latch will let the striker come forward only if the latch is depressed. The chewed up area on the striker is from my mistaken assembly and a ton of testing trying to figure out what I did wrong.
Here’s another angle. The striker can only travel forward if that blocking latch is depressed – in the photo, the latch would be pushed down out of the way. In the Uzi with the bolt oriented the normal way, we would say the latch is being pressed upward.
10] If you look at the above photo, the striker system. The lower L-shaped bracket is the “Striker Guide”. Thestriker spring base and the striker are held in place by a roll pin. The return spring slides over the striker spring base as shown above.
11] Take the guide rod and spring from the kit and snip the fiber square board off the end. I used diagonal cutters and when I made my first cut the little board fell right off.
12] You then insert the recoil spring into the bolt and rotate the firing pin base while inserting the assembly into the bolt. The white is Tetra Firearm Grease. If it slides, grease it. If it rotates, oil it. You want this system to be well lubed to help it wear in.
13] Here is the whole bolt assembly with the recoil buffer at the end. Now this assebly is slid into the Uzi buffer end first. It takes some maneuvering to the recoil block into the rear and then the bolt nestles down.
14] The top cover is then installed. I used a 120 grit flap sander bit to slightly bevel my top cover to the catch can close and the top is really tight. The top black cover has the bevel in the photo below – it doesn’t take much. If you have any questions about what needs to be done to prepare the top cover for semi-auto use, click here.
14.1 – Added 7/2/18: I found out that you really need to fit the top cover. If you take a feeler gauge, you should be able to insert a 0.005 gauge between the bolt body and the top cover at the ejection port and meet little to no resistance. However, if you insert a 0.015 gauge, you should feel some resistance – not a complete stop but firm resistance. At 0.005, the gap is too small and you risk the bolt body binding and not travelling fast enough or far enough resulting in ejection and feed problems. The cover is very easy to adjust. I did a more detailed blog about testing and adjusting the cover – click here.
15] Now function test it to be safe. Do this with the weapon unloaded!!
Try to move the selector switch to Full Auto, which is all the way forward. It must not be able to move past semi-auto. If it does slide to the forward full auto position, you must fix it. If you haven’t done so, you need to install or fix your blocking tab that should be welded in the grip frame – click here for details. If you welded in a blocking plate, it may be too thin or too short. Regardless, you must figure out what is going on and fix it immediately. The ATF says the selector must not move into the full auto position.
Move the selector to semi-auto (the middle position), hold the grip safety, cock the weapon and squeeze trigger – you should here it dry fire with a real solid clunk sound. Life is good. If there is a soft click, the striker system did not cock – check your sear to make sure it is protruding into the receiver.
Move the selector to semi-auto (the middle position), DO NOT hold the grip safety, cock the weapon and squeeze trigger – the weapon should not fire. The Uzi should only be able to fire if on semi-auto and the grip safety is held. Check your pins and that the grip safety bar is sliding properly.
Move the selector to safe (all the way to the rear), hold the grip safety, cock the weapon and squeeze the trigger – the trigger should be blocked and nothing should happen. Turn the safety off and the weapon should fire. If it does not, check the pins and the selector bar can move into position properly and block the trigger.
Last, move the selector to semi-auto, hold the grip safety, squeeze the trigger (do not release it) and cock the weapon while holding the trigger in. We want to ensure the disconnector grabs the striker assembly. Now, release the trigger and squeeze it like normal. You should here it dry fire with a loud clunk sound and that is what you want. A light click is just the trigger and disconnector moving around and means the striker went back into battery vs. being retained. Something is off with the geometry – something is bent, you forgot to secure the grip frame with the takedown pin, etc.
If your Uzi passes the function tests, then proceed to test firing. I’d recommend securing the carbine in a stand and test firing with a string vs. holding the weapon. Also, only load one round in the magazine at a time and inspecting the carbine, especially the barrel, to make sure the first round fires and the case is ejected. Look for dings or tears in the case. Make sure the bullet didn’t get stuck in the barrel. If things are looking good, put two rounds in the magazine and test the overall cycling of the weapon. Again, check the case for any big gouges, scrapes, etc. When you are satisfied that the weapon is functioning correctly, then and only then try more and more rounds of ammo. I would go from one, to two, to three to five and to 10 before I tried a full clip. You do not want to have an uncontrolled full auto dump happen so carefully test the Uzi.
I had a lot of fun building mine. I added a Vortex Venom red dot that I really like so far plus an original Uzi green sling. Here are some photos and as mentioned the light and rail are off the weapon at this point.
I hope this helps and if you have any suggestions, please let me know.
I’ve used John Norrell’s Molyresin finish for years and like it. It’s easy to apply and quite durable. My preferred approach is to abrasive blast a steel surface, parkerize it and then apply the Molyresin and bake it on. There was one challenge this time though – it was below freezing and a snow storm was going on so I opted to just blast and apply the finish. This ought to hold up fairly well. With AKs, I am always fighting the selector lever scraping the receiver but don’t have that situation with an Uzi.
1] Clean everything with brake cleaner or acetone. I use a ton of brake cleaner. Also, be sure to wear nitrile gloves to avoid getting oil from your hands onto the clean parts.
2] Here’s a time-saving trick – the Uzi’s original parts were parkerized. Just clean anything with a good parkerized surface thoroughly but do not blast it off. If the “park” is worn away, proceed with blasting the surface. The reason is simple – parkerizing creates a surface that the Molyresin can really adhere to when baked on – even more so than blasting alone. Molyresin will not last if you just spray it on a smooth surface and bake it so don’t even consider doing that. In short, at least blast the part including all edges, corners, flat places, and so forth unless they are parked already. If you have the capacity to park parts [click here for a tutorial], do that and then apply the finish.
3] I used to use the Harbor Freight air brushes but have had a ton of problems with them failing so this year I invested in a nice Paasche H-series airbrush after hearing good things about them over the years. The quality is night and day better. I read a bunch of confusing junk on the Web about guys questioning how to hook up their air line. After buying the kit from Amazon, I simply applied quality PTFE tape to a male 1/4″ plug with a male 1/4″ NPT end and screwed to Paasche air line on to it. Done.
Paasche supplies a small bracket for holding the airbrush. I screwed it onto some scrap plywood so I can move it around as needed:
Also, I am really obsessive about clean air – I run a high-end filter system in my shop and still put a screw in filter just before the air brush’s air line just to play it safe. If you run your air brush off your home compressor, you definitely need to do this.
Another tip – don’t use cheap Teflon/pipe thread tape. I’ve had excellent luck with the following:
4] John has really good instructions online for applying Molyresin. I bought a quart of semi-gloss black for the Uzi build plus I plan on using it for a few other projects I have planned thus I bought the big bottle. They say an 8 oz bottle has enough Molyresin to coat 2.5 AR rifles. I used a tad over one ounce on the Uzi but I’m inefficient with my application because I am spraying all the little parts also. You have a ton of adjustments you can do when applying a finish via a paint brush so your actual coverage will vary. I have a simple theory though – I’d rather have left over finish than be in the middle of something and run out!
5] You need to preheat your parts to 150F. This allows the solvent to evaporate very quickly. Since the Uzi parts are all relatively small, I used my portable roaster oven that I bought at WalMart on sale. Oven thermostats are notoriously inaccurate so use a good thermometer to confirm the actual temperature. I use a Fluke 62 Max Plus due to my work with plastics and steel. My oven runs about 47 degrees cooler than what the dial heat setting claims for example. At any rate, I start preheating my parts while I get m airbrush ready. All the cleaning and surface prep is done at this point and I am wearing either nitrile gloves.
6] So, I used the size 1 tip that was installed in the Paasche brush and set the air pressure to 20 pounds and then dialed the tip in and out until I got the spray pattern that I wanted. One of the nice things about the Paasche is that the company stands behind their products – you can ask questions, lots of people have written about them and you can also download the manuals. I can tell you one thing, I am never going back t the Harbor Freight brushes now.
7] Shake the heck out of the Molyresin to get the settled pigment into suspension. Don’t just shake it once or twice – make sure the cap is on and shake vigorously for 20-30 seconds. Molyresin has pigments that are carried along with the solvent that must be deposited onto the metal and then baked into place. The liquid solvent is really just a carrier.
8] I apply the Molyresin in several coats until I have a uniform color everywhere. One trick I learned years ago is to take a cardboard box and cut slots in it to push in screws to paint their heads. Be sure to periodically shake your airbrush to keep the pigments in suspension.
9] For the barrel, I do install rubber plugs in the ends of the barrel to prevent finish from going inside. You can buy these tapered silicone rubber plugs from a variety of sources and reuse them. My current batch is from Amazon.
10] When you are done, clean the airbrush with MEK. One thing I do is to clean the little supply bottle first, fill the bottle with MEK and then blow in through the brush to clean the internals. Note, use MEK in a well ventilated area as you do not want to breath those fumes.
11] Place the parts in the oven at 300F for one hour to actually set the phenolic resin. This temperature is critical as nothing will happen if you heat to a lower temperature and you may affect the sheen of the finish if you go hotter. Again, use a good thermometer to make sure you are at or just over 300F – allow for the accuracy of your thermometer in other words. If your thermometer’s rated accuracy is +/- 1% then shoot for 303-305F for example or even a tad hotter but not less. The one hour is also a minimum. Boosting the temperature and reduce the time is not recommended.