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AR Repair: The Frankengun 2

AR repairs are always an interesting story. Had a customer bring in this AR rifle for repair. Supposedly built and used by a friend who later sold it to the customer. His first “Red Flag” should have been when the “friend” sold him the rifle without the bolt carrier group. Apparently the gold colored bolt carrier group was more important to the friend than to my customer.

Yes, those are red anodized parts that you see. The customer initially wanted me to find a red bolt carrier group to match those parts. While there are red bolt carriers on the market they are intended for “gamer” guns looking to have the least amount reciprocating mass in order to reduce recoil. Unfortunately this makes the rifle very ammunition sensitive. The use of an adjustable gas block is almost mandatory to keep the gun from self-destructing in short order. All of these factors combine to make the gun less than 100% reliable when it starts to get dirty. Since the customer was considering this rifle for self-defense, and training for duty use, he accepted my recommendation for a standard bolt carrier group.

As you can tell from the above images it did not take long for the problems with this build to become evident. The stock is clocked about 10-15 degrees.

The gold line is the lip of the receiver extension. (AKA buffer tube) It should be to the left of the buffer retainer. This style extension uses that lip and the buffer retainer to keep from unscrewing from the receiver, if installed correctly.

Here you can see a several issues. First is the lack of staking to hold the castle nut in place. Since the aluminum endplate would not have staked well it’s better that they didn’t try. Because the gold color of the buffer tube can be seen through the staking slot it tells me a few things. One that the slot goes all the way through, which means that any staking would not be supported. The slot should be cut at an angle and be only 1/2 -1/3 the depth of the castle nut. Second is that there is nothing between the aluminum tube and the steel castle nut. So this rifle would be susceptible to galvanic corrosion. Think of it as being “rust welded” together. Without any sort of lubrication for the castle nut, the torque reading would also be suspect, if they used a torque wrench at all.

Hard to tell from this view, but this endplate not only has a QD socket it has loops on both sides for clip on sling attachment. It does not look like it was used with a sling very much since it still looks nice. The steel attachment hardware most slings use would have really chewed this up quickly.

Staying with lower receiver. The legs of the hammer spring are under the pin for the trigger and are digging into the floor of the fire control group pocket. The trigger pin has slots cut into it just for the hammer spring legs. That’s what hold the trigger pin from walking out of the receiver.

Speaking of pins walking out. This build unnecessarily used “anti-walk” pins with a standard mil-spec trigger. The brilliance of the standard trigger and pins is that it can be disassembled in the field without tools should it be necessary. Popped primers can end up in the weirdest places. This rifle will need a very small, and easily lost, allen wrench to remove.

This is personal preference, but I would have put long serrations on the top if possible. It was not very comfortable to actuate the safety configured this way.

That’s the end of the issues that were found with the lower. The magazine latch was one turn out from optimum, but that’s an easy fix. All of the issues with this rifle were found upon initial check-in, it never made it to the bench for a more in depth inspection.

The upper receiver had issues of it’s own. Let’s take a look at those.

While this is a good linear compensator, it doesn’t have much room around it. That will be an issue with some of the following pictures. This handguard is one of the few on the market that is over 16 inches long, so it covers the wrench flats over this muzzle device.

It’s hard to see but gas block is pressed up against the inside of the handguard. That defeats the purpose of the handguard being free-floating.

While the gas block may be rotated on the barrel. It’s more like that the handguard moved against the gas block and possibly the gas tube. I could not find any sort of anti-rotation feature on this handguard.

Another view of the tilt in the handguard and the rather unusual placement of the off-set foldable rear sight. I assume the builder kept what ever optic was on here along with the BCG. But I can’t figure out why it was placed in such a way as to partially block the ejection port and it’s door.

Now most of the above problems would be easy to fix if I could get the handguard off. That’s where the real problems start.

These are close ups of the screws used to attach the panels using the built in M-lok slots. That in and of itself would not be a problem if I could be certain that they were torqued properly. Since this is a metal handguard and they used metal accessories the screws should only be torqued to 35 in-lbs. The screws in the last 3 pictures are not square leading me to think that they have been severely over torqued. In one of the pictures there is evidence of an accessory having been over torqued and then removed. Others show that the picatinny rail has not been installed flat to the handguard. Because of the possibility of these screws not coming out easily, I built some extra time into my estimate.

Some of these sockets are badly damaged, making the removal of an over torqued fastener even harder.

Having found these issue just by looking the rifle at the dining room table I knew that the entire rifle would have to be completely stripped down and rebuilt to ensure that all the proper assembly procedures were followed. That would be the only way to make sure that things like the barrel nut and gas block screws were torqued correctly. Most of the time I could just remove the handguard with the accessories attached, but remember how little room there was between the muzzle device and the handguard. Just remove the muzzle devise first then right, no go. The handguard is 16.5″ long and so is the barrel. That means I can’t get to the wrench flats. Because of the recipe of parts that were used I would have to peel all the layers off like an onion.

There were issues with the design of the handguard. The M-lok slots on the bottom were unsupported, because of the overly long ventilation cuts on either side of them. I found one of the slots showing evidence of bending, most likely from having had a vertical foregrip installed at one time.

I did an estimate for the work including new handguard, bolt carrier group, endplate and other parts to get it up to a standard that I would feel comfortable with letting it leave my shop. After doing the math, it was almost the same price as if I were to build him a brand new upper with all new parts, and make the few changes to the lower.

Unfortunately the customer had not budgeted for this, and chose to pick up his rifle with out any work being performed. I do not have any after pictures or performance improvements to show you for this project.

So buyer beware, if that rifle seems to good to be true, get it checked out by someone. Hopefully this article, and the other Franken Gun article, give you some useful information to evaluate that used AR you have your eye on.

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AR Repair: The “Frankengun.”

This is an AR pistol that a customer picked up at a gun show. He brought it to me to look over and address any issues that it may have. While it may look fine at first glance, I would not be doing this article if it was.

The Frankengun AR15

The first thing that I noticed was that the castle nut was not staked. While it is not absolutely necessary to stake the castle nut, it costs nothing and doesn’t take long to do. If the person doing the assembly doesn’t care to take the time to do this simple step what else did they skip?

Well apparently using a proper 3/4″ inch wrench to attach the flash hider was just too much. Not exactly sure what they used. Pliers of some sort is my guess. Channel locks or locking pliers most likely.

For those of you not familiar with this platform, the gas tube should NOT go down towards the barrel.

No clearance for the gas tube. Not a problem for the person doing the initial assembly, just use a rabid beaver to chew a hole in the handguard.

What goes down must go up……………….eventually. There are supposed to some bends in a gas tube. This is NOT one of them.

These are what I was able to find by just doing a quick inspection on the outside. It didn’t get any better once I opened it up.

By the looks of the buffer, that beaver was not full after chewing on the handguard. These marks are the result of the buffer hitting the retainer during firing. The buffer should only touch the retainer when the upper and bolt carrier are not in place. The bolt carrier should push the buffer off of the retainer when closed. There are a couple of ways to check for that this. With both the takedown and pivot pin pulled out the upper should be pushed away from the lower by the buffer. Another way is to remove the charging handle, replace the bolt carrier, close the upper and you should be able to see the buffer move. I tried both of these tests and it passed. So here is another short cut taken by the builder. They took a chewed up buffer that they didn’t want and put it in a gun that they were getting rid of. Are you starting to notice a trend that started with the lack of staking on the castle nut.

This is the back of the bolt carrier. There doesn’t appear to be any obvious burrs or deformations that would cause the marks seen on the buffer.

Staying with the bolt carrier, I checked the screws holding the gas key on using the reverse torque test. Proper forward torque should be approximately 55 in-lbs. The reverse test starts at 25 in-lbs. One of the screws came loose at that range. The next step is 35 in-lbs. The other one failed here. The staking here was also almost nonexistent. If your gun shows signs of being undergassed, and you see carbon built up at the front edge of the gas key then have it checked out.

You can see by the shiny spots that this gas key was starting to move on the carrier. There’s a little carbon built up around the gas port but it has not made it to the sides of the key, so there were no outward signs that this was coming lose. This issue was caught before it became a real problem. Lose screws have a way of becoming broken screws.

Results of the first few passes on a diamond plate to “deck” the gas key. If I had just simply tightened the screws back down it may have still leaked in the future.

Finished “decking” the gas key. We are limited to fixing only this piece because of the way the carrier is machined. I use a bearing retaining compound to fill in any remaining imperfections in the mating surfaces.

These pictures show the retaining compound squishing out, and the new “OCKS” used to secure the gas key. (Optimized Carrier Key Screw from Michiguns Ltd.

Using a MOACKS Plain also from Michiguns Ltd. to properly stake the gas key screws.

(Mother Of All Carrier Key Stakers)

The OCKS give a place for the metal that is displaced by the staking a place to go and keep the screws secure. The burrs that caught the fibers from the rag were eventually removed.

Original extractor spring and insert. Since there were other suspect parts in this gun it just made sense from a reliability standpoint to replace it.

In the image to the right the original extractor spring and insert is on the right, the Sprinco 4-Coil spring and insert are on the left.

Next I checked the gas rings, they seemed fine and were reinstalled

This is the ejector after polishing. Didn’t take a before picture, but it had a pronounced projection from the machining. It would have eventually scraped brass from the bottom of the case. That could have ended up down the bore that the ejector is in causing poor performance or even a malfunction if the case is not pushed clear of port fast enough.

Original ejector spring on the right, new on the left. The original may have been fine, but for few dollars a new one cost, it was better to replace it. With the ejector and spring out I checked the headspace and it passed.

The next check I performed was to see if it actually has a 5.56 NATO chamber and throat. This gauge from Michiguns Ltd.checks for that.

To start I “Sharpied” the end, to show if there was any interference.

The gauge is then pushed lightly into the chamber. It should fall out if the throat is the proper size. Go figure it got stuck in this one.

The white line in the ink is where the gauge made contact with the throat. This barrel did pass the “plunk” test with some factory ammunition so I didn’t try to fix this.

If you look at the feed ramps in these photos you will see that the center locking lug protrudes into the feed ramps cut into the upper receiver. This can cause malfunctions by catching either the bullet tip or the edge of the case as it’s trying to feed into the chamber. There are also some machining marks still visible.

The major work on the right side is done, and the left is almost done.

Here the ramps are all finished. Nothing to snag on.

Judging by the carbon ring it appears that the gas block was slightly misaligned.

The barrel is not dimpled so there was no place for the set screws to index in.

Using a jig I added a dimple. The picture is before I reblued the surface.

New gas block and tube installed.

New gas tube on top. Original on the bottom. Muzzle end would be on the left.

Closer look at the chewed up flash suppressor. In this image you can see that the crush washer has been installed backwards. The muzzle device was not tightened to specs either.

This is why I couldn’t see the crush washer with the handguard installed. Speaking of the handguard. The following images may be disturbing, if you care about how your firearm is assembled.

This is the bottom of the handguard. Not really sure why they went after this area. Probably the mildest definition of a mistake. It gets worse from here.

You were warned.

After looking at this closer. It appears that this handguard is for a blowback operated platform since it doesn’t have channel for a gas tube. That didn’t deter someone from making one. Not sure how long it took to make this disaster, but it had to go. Now that the upper and barrel are fully disassembled it is time to start bring this thing back to life.

The gas block was previously installed. Here is the new Midwest Industries Pistol Blast Diverter.

Installing the new handguard. A Midwest Industries 10.5″ Slim Line Handguard.

Back up Iron sights reinstalled.

Completed upper with Holosun Red Dot installed. This is much better.

Next was to address the lower receiver. For the most part there were no major issues found. Just the buffer and the non-staked castle nut.

The roll pin for the trigger guard was a little above the surface of the ears. That was a quick fix.

The hammer and trigger springs were okay, so they were reinstalled.

Added a set screw for the take down pin retaining spring and detent. This will keep the spring from coming out unexpectedly, should the endplate be removed.

Torqueing the castle nut to 40 ft=lbs.

Castle nut staked in 2 places, as per the manual.

Here’s the completed rifle getting a final cleaning before being returned.

Added a Blue Force Gear Sling and Midwest Industries Swivels.

Business end of the Blast Diverter.

Streamlight Pro-Tac Rail Mount HL-X with Laser. 1000 Lumen light with built in laser.

The finished product. Short, light, reliable, what else could you ask for.

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Worked on an AK

This is what it looked like when I started. Pretty simple, had a few internal upgrades and an aftermarket muzzle-brake.

The customer wanted me to add a side mount for a scope.

Had to break out the power tools to modify some screws to make it work.

The middle is the original, right is from the store, left is filed down to fit the holes in the mount.

Mount finished. Didn’t use the middle hole because of interference with internal parts.

Added a Magpul AKM forend.

Added a Magpul Stock

Here’s the finished rifle with red-dot and sling. QD sockets, sling and cheek riser are on back-order. Much like most projects it;s a work in progress.