Soup to Nuts 4

From Soup to Nuts, Building Building an AK-47: Part Three Three - Installing Installing the Rails - Surplusrifle.com Surplusrifle.com Page Page 1 of 17 17

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Article by Rob Summerhill (RapidRob) Adobe PDF Downloadable Version of Article Editor's Note There will be several more articles in this series published very shortly including different variations covering different methods for assembly. The different methods covered will range from a standard screw based build to a more complex rivet build.

Note: Removing the Barrel will need to be done at this point if you are to using rivets to hold your rifle together.

From Soup to Nuts, Building an AK-47: Part Three - Installing the Rails - Surplusrifle.com Page 2 of 17

There are several ways to remove the barrel. The easiest way is with a hydraulic shop press. While a two-pound sledge- hammer and drift punch can be used, it is not easy or fun to do. You also risk damaging the barrel or the front trunnion while using the hammer method. First off you need to remove the barrel pin. This large pin has been set in place by the factory with a lot of force. Most pins have galled the barrels steel and have jammed in place or rusted from normal use. You will need to support the barrel and the front trunnion using care to prevent any miss alignment. After you have verified all is well, you will start to apply pressure to the face of the pin. All pins on the AK are driven from the right side going to the left. As you apply pressure you will hear a loud pop as the pin has started to move in its hole. Continue to drive the pin clear of the hole.

Once the barrel pin has been removed you may move on to pressing out the barrel.


Note that the barrel or its pin may have gouge marks in or on the steel. This is normal and was done by the factory and not you. The removal of the barrel from the front trunnion is an easy step at this point. You can use the hydraulic press of a hammer and a brass drift punch. I used the press and a series of brass rods slightly larger than the breech to shove the barrel forward. You may want to make a “witness mark” on the barrel and trunnion to help you align the barrel when reattaching. Once the barrel is clear of the trunnion you may want to polish the outside of the breech area to remove any gouge marks. Do not be tempted to reduce the outside diameter of the breech. This barrel is made to be a tight fit in the trunnion. You can now drill/drive out the rivet stubs in the trunnion. Make a note of the recesses in the front and lower rear portion of the trunnion. There are two sets of holes, which take their own type of rivet. RIVITING

There are several types of riveting tools out there to buy. One uses a hydraulic press, another compressed air and lastly, a tong type of tool made from 24” bolt cutter.


The tong tool is inexpensive ($40.00 normal) very powerful and easy to use. The fellows who make these tools have done all of the milling and fitting of the rivet jaws to allow the setting of the rivets in the AK receiver. All you need to do is provide the rivets and the elbow grease. A note on rivets. There are many folks selling the rivets for the AK type rifles. Some rivets are real mil-spec, others are poorly made. Some are too soft, others too hard. What to buy? Make sure to check out the other web sights on building the AK and ask who has the best rivets? Expect to pay $9.00- $12.00 per rivet kit. Never use aluminum or brass rivets. Stainless steel can be used, but may not hold a paint finish.


Front Spacer and Rivet

There are several lengths and type of rivets that are needed for completion. There are rivets for the top holes of the barrel trunnion, bottom trunnion hole, the front spacer, and the long rivets for the rear trunnion. The front spacer/support rivet is very flat on one side and needs to be to clear the rifles safety lever on the right side of the receiver.

This is the only rivet that you can place on the wrong side of the receiver, pay attention. Make sure that the rivet holes in your receiver will allow the rivet to pass into the parts being riveted. You do not want slop in these holes. The rivet needs to pull the parts together tightly and with no play. At this time you need to verify just where the holes line up with your barrel trunnion. It is very important that the front trunnion is even with the front of the receiver. If it is forward or


back just a bit, you will have magazine fitting problems.


The receiver has to be trimmed to fit both trunnions and has to be bone by hand fitting. All the receiver flats are made oversize and require these steps. A Dremmel tool with thin cutoff wheels is easy to do, a milling machine would be ideal. The front trunnion has two female grooves cut into the trunnions sides that will hold the top of the receiver’s side rails. You need to remove excess metal from the top rails but leave just a very slight radius that will fill the female slots. Once you have done this, the front trunnion can be riveted into place. The top holes take the four ½” long rivets; the two lower holes take the short 3/8” long rivets. These rivets have to clear the magazine. Setting the rivets is easy but can be improperly done if not careful. Clamp the front receiver into place. Use a drift punch to align the holes and install one rivet into the upper holes. Using the milled tong tool jaw, place pressure on this jaw to keep the rivet flush with the side of the receiver. Make sure the back jaw in on the exposed shank of the rivet you are setting. Apply a constant force on the rivet and it will crush and bring the parts together tightly.


The trunnions have a recess to allow the crushed rivet to be slightly below flush. If you cannot do this on the first crush, adjust the tong tool to allow you to do this. If the rivets are not below flush, you will not be able to mount the barrel in the trunnion.


Continue with the other five rivets. Same goes with the lower short rivets, they must be below flush. You have now mounted the front barrel trunnion. Double check the two lowers rails and make sure the bolt and carrier will move and lock up with little force. Bending the two lower rails up/down slightly may need to be done to aid alignment. We now need to mount the trigger guard and magazine catch assembly.

From Soup to Nuts, Building an AK-47: Part Three - Installing the Rails - Surplusrifle....

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There are jigs you can buy to allow this step to be done easily. If you don’t have one you will need to make a single rivet setter and crush punch. I will use the jig. First off, inventory


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all of the trigger guard parts. You should have the trigger guard, a spacer plate with a bent metal tab on it, and maybe an inside rivet retainer (under folder) the jig I am using requires a hydraulic press or a steady rest and a heavy hammer. I am using a Harbor Freight 12 ton press. The jig comes with a pair of small metal plates that will crush the rivets in the triggers corners. They can only go in one way to work.

The jig will allow you to crush four rivets at one time. You align all the parts, making sure the safety stop plate is on the right side facing up, insert the rivets through all the holes and parts, set the crush plates, double check every thing, and start pumping. The rivets will crush and pull in all of the parts tightly onto the receiver. The rear trigger guard hole will be done the same way. You may need to adjust the crush plates to get an even crush on the rivet shank.


You have now mounted the trigger guard and magazine catch.

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Now to the front support. There is much discussion on just what is the proper length of the front support tube that sets the width of the inside of the receiver. The makers of the flats and some of the companies say that the total distance of the inside, receiver wall to receiver wall, taking into account the thickness of the two lower rails is to be 1.250” This number is just a general number to keep in the back of your mind. You will have to cut/grind down the two upper rails to allow free movement of your bolt carrier and mount the top cover. Each bent flat will very slightly and will need to be hand fitted. I have seen front support tubes 1.177” long, 1.450” long, and 1.090” long. It’s your measurement that counts. The two walls of the bent receiver should be perpendicular and show no signs of forming a “Y “shape. Only you will know what will work for your kit and bent flat. Most of my kits did use a tube 1.177” long. This tube is very important for the safe use of your rifle. It provides two important features. One is that it prevents the hammer from striking and bending/breaking the ejector. Two, it prevents the receiver from twisting during handling or firing.


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You will need a hard steel surface (flat vice, anvil, etc.) to set this rivet and a ball peen hammer. Insert the long flat head rivet from the right hand side of the receiver through to the left side of the receiver. How much that sticks out is up to you and the width of your receiver. 3/16” is about good. Place the receiver onto the flat steel of your vice, anvil, etc. and using the ball peen hammer’s ball head, strike the exposed shank with a glancing blow. You want to draw the metal out into a circle. Once you have a round like head on the rivet shank, use the flat head of the hammer and set the rivet. The formed head should be at least three times the diameter of the rivets pilot hole to hold properly.

Make sure it is tight with no play in the support tube. From now on every measurement you will make to finish this rifle will be off of this front support dimension.


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The rear trunnion will need to be removed from its half of the cut receiver. Use the same method you did for the front trunnion to do this step. The rear trunnion has two long rivets (folding stock will have several types) that are made of steel that is tempered softer in the center portion. When the factory set the rivet, the rivet formed a “Z” shape inside of the holes of the rear trunnion. You will not be able to push these rivets out. You must drill the rivets through their length and drive out the outer shell of the drilled rivet stub. Doing the drilling using a hand held drill can be done but it’s very tiring and your hole may not be straight. A drill press is the tool to use. The type of drill bit you use is up to you. The steel in the rivet stub is difficult to drill using even the best bits you can buy. Go slowly and keep the bit well lubed with good cutting oil. If you rush you chance snapping off the drill bit. Of all of the steps building the AK rifle, this one will take you the longest time. Expect to take 15 minutes per hole to drill out the old rivet You now may want to test fit your rear trunnion into the trimmed receiver. All receiver


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holes should line up.

Now, to mount the rear trunnion. Most, but not all rear trunnions will mount with the long, non-flat headed rivets. Your kit type will be the deciding factor on whether you use a ball peen hammer or rivet tong tool to set the rivets. All of the above steps are used here also. Once again the rear trunnion will be flush with the rear of the receiver. Note that the trunnion also has a female groove cut into it. You will need to trim the receiver and leave enough metal to ride in these grooves. The rear trunnion will dictate just where and how wide the notched receiver top will be to allow you to install/remove the bolt carrier for this rifle. Do not guess this measurement. Too wide and your bolt carrier will jump out when the rifle is fired. We will cover this step later on.

You have now installed the two lower rails, and riveted the trunnions and front spacer in place. A test fit of the magazine is needed at this point. Failure to do this step will result in a rifle


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that will not function normally. Most of the TAPCO flat kits have parts that are too large to allow normal operation. These parts will have to be hand fitted. The lower right hand rail will control how tightly the magazine will fit. Make sure to note how far the magazine will enter the well and remove a little metal at a time off of this rails lower bend. Slight trimming of the front of the trigger guards latch plate may also need to be done. Take your time and be sure what you are trying to do. Just a little too much metal taken off will ruin the rifle’s normal operation. Other than mounting the barrel to the front trunnion and trimming the excess metal on the top rails, you are close to having a functioning AKM rifle.

Next: Part 5 Mounting the barrel and trimming the top rails. Article by Rob Summerhill (RapidRob) Adobe PDF Downloadable Version of Article

Soup to Nuts 4

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