ПРОЕКТ КАЛАШНИКОВ
Ствольная Коробка —
Точечная электросварка, заклёпки и термической обращение

Receiver Fabrication — Riveting and Heat Treatment

Ствольная коробка, stvol'naya korobka, the "barrel box" as the Russians call it. We have already bent it and milled the top rails, producing what you see below.

Now it's time to spot-weld the internal rails into place and rivet the front and rear trunnions and the trigger guard into place. Then we will heat-treat the areas around where a few of the cross-receiver pins will be mounted.

This is one in a series of pages about the history and reconstruction of the Автомат Калашникова 47, Avtomat Kalashnikova 47 or Kalashnikov Automatic Rifle 1947 Model, designed by Mikhail Timofeevich Kalashinikov in 1944-1946. It was originally manufactured at the Ижевский Машиностроительный Завод, ИЖМАШ or Izhevskiy Mashinostroitel'ny Zavod in the western Urals.

Very thoroughly clean the receiver and internal rails using acetone. You must remove all the oil before spot-welding those rails into place!

We have spot-welded the internal rails into place.

The welds need to be cleaned up with a small sanding wheel to remove the small flecks of metal.

These welds further forward on the right side came out a little cleaner, but they still need to be cleaned up.

A customized fixture provides a way to install the rivets.

You also need a simple but customized striking tool to install the rivets.

We are ready to rivet a rear trunnion into place. The rear trunnion uses two long rivets. The first one is already in place, the second one is ready to be hammered.

Start by tapping the rivet with a ball peen hammer. It is important to use the right amount of force. You don't want to try to mash it all the way down with a few extra-hard blows!

Once the head starts to mushroom, use a rivet driving tool.

The head mushrooms further out. Continue to strike it with the driving tool with the cup at its end.

This rivet is finished!

Here is the result. We are looking at the left side of the receiver.

The three rivets farthest to our left hold the front trunnion in place. They are short rivets, three on each side, passing only through the receiver and the outer face of the trunnion.

The single rivet above the front (our left) end of the trigger guard passes all the way through the receiver, passing through a steel tube.

The two rivets farthest to our right hold the rear trunnion in place. They are two long rivets, passing all the way through the trunnion and both sides of the receiver.

Here we are looking at the right side of the receiver. One rivet holds the rear of the trigger guard in place.

Two rivets on either side hold the front of the trigger guard and the magazine catch in place.

You can see the single rear rivet and two of the front rivets on the trigger guard and magazine catch.

Looking through the magazine well, you can see part of one of the internal rails.

Here we are looking through the magazine well. You can see the central rivet passing through the tube across the receiver.

You can one of the internal rails at left here. The bolt was assembled into place and tested for fit.

There was not enough clearance for the bolt to translate forward and back. A comparison measurement was made to a commercial receiver, and metal was very gradually removed from the tab on that rail with a file. A small amount of metal would be removed, and then the bolt was tested for clearance again.

Here is a view looking down into the receiver, at the internal ends of the rivets holding the trigger guard and magazine catch in place.

Another internal view shows both internal rails. These internal rails were already heat treated. If they hadn't been, that would have been required before spot-welding them into place.

Here you can see the internal ends of some of the rivets holding the front trunnion in place.

These are the most difficult rivets to install. A customized striking tool is definitely needed for this!

Here we are looking into the front trunnion, where the chamber end of the barrel will be inserted. A pin pressed through the hole across the top of the trunnion, seen on top at right here, will lock the barrel and receiver together.

This is the other side of the front of the receiver, with a flash rather than ambient light as seen above.

The real Bubba method here is to use something like 10-32 machine screws! You can probably imagine how quickly they would work loose when the gun was fired.

The remaining holes need to be heat treated. The goal is to make the steel harder, but not brittle.

The steel was relatively soft, allowing us to bend the flat into place and allowing dimples to be stamped into the original flat. For the most part, the steel is of appropriate hardness. However, we need to harden the steel around the three holes that mount the pins holding the moving parts of the action.

The trick is to take the steel up to a certain temperature and then quench it by dropping it into the pan of oil. That makes it hard, but leaves it brittle.

Then, take it back up to a slightly lower temperature and hold it there for a few seconds, allowing the newly formed grains to release their stress. Then dunk it back into the oil.

There's a real art to the heat treatment. With experience, the temperature can be judged by the color.

The result looks a bit ugly for the time being. I have removed the scale from the burned oil with a small high-speed sanding disk.

The next step for the receiver will be bead-blasting and parkerizing, which will form a protective outer layer on the metal and clean up the appearance.

Next step: Restoring the wood stock

© Page author Feb 2012.