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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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