Demill - Part #2
Demilling a STEN Mk III parts kit
Please read through the directions before starting the process. I cannot stress enough the need for proper eyewear. The mask is to avoid breathing in dust as you are grinding. Do not rush through the procedures, take your time and you will be rewarded in the end.
STEP 2 – demilling the BARREL & TRUNNIONS:
Next up on my list was the barrel.
We’ll start to identify what we will be removing. Rear rivets supporting the handguard & rear barrel trunnion.
(click on any of the pictures for the larger picture)
Front sling swivel. This one require a bit more work. We’ll discuss later on.
And of course the front rivets for the front barrel trunnion.
Let’s start by removing the rivets that are holding the handguard & rear barrel trunnion. Once you have removed them, you should have something that looks like this.
Using the chisel, carefully begin to separate the handguard from the receiver. After you remove the handguard, put it away for safekeeping.
Next grind down the rest of the rear barrel trunnion rivet heads on the left side of the receiver remnant.
Finished views of the rear barrel trunnion, after rivet heads were ground off.
Proceed to do the same with the front barrel trunnion rivet heads.
I actually did this towards the end, but in hindsight, it should be done prior to the removal of the barrel.
Mark and cut off the receiver around the front sling swivel.
Notice that the extra sheet metal that was cut was generous. This will later be trimmed with the Dremel. Go slow and only remove what is needed so that when you reconnect it to your new build you have enough metal for a good weld.
Now we get to an odd event. I had previously demilled a MK III kit and there were 8 rivets in the front barrel trunnion section. Some were exposed and some were not. I am not sure if that was a different variant of the Mk III or what it was. Thinking that that was the same here I proceeded to remove the shell housing.
On this Mk III kit, there were only 4 rivets in total. In the 8 rivet model, the barrel had 4 indents in which 4 unexposed long pins were pressed into the front barrel trunnion and holding the barrel in place. The other 4 were holding the sheet metal housing to the front barrel trunnion. This demil only had the 4 rivets.
Therefore for sake of work involved. If your kit looks like this, then first try to push the rivets inward with the punch. Do the same with the rear ones and the barrel assembly should slide out. You may need to push it out with a piece of wood and a hammer. Go to the end of this section to see how the rivets were pushed out. If however, it does not budge than proceed with the following.
Next we will focus our attention on the barrel housing.
You will begin to cut along side the left or right of the top.
From the front mark ¾ inch inward. If your nervous go 1 inch inward. This is the stop point. Yours won’t be precut like in the picture. I needed to cut it to find out how far it went.
Than measure 5 ¼ from this point rearwards. This is your second stop.
Cut a slit between these two points. Do not cut too deep, just enough to cut through the sheet metal. Remember there is a barrel underneath.
When you are ready to cut above the front and rear trunnions, go slow and be careful to just cut the sheet metal and not into the trunnions. See pictures that reference the measurements.
By now the whole length is cut. Place the barrel assembly in a vise. Using a big flathead screwdriver or similar, begin to separate the sheet metal.
You will notice in the above picture how the sheet metal begins to come off of the rivets.
Continue. You may have to use two bars or screwdrivers if the assembly starts rotating while in the vise. I would not recommend clamping down harder on the vise but just to use another bar.
It should look something like this. Don’t remove the assembly from the vise yet.
While still in the vise, use a pipe wrench or similar to finish the edges. Do both front and back.
This is what it should look like. You just want to bend it open enough to clear the rivets.
You can re-clamp it in the vise like this.
Continue with the pipe wrench until you have this.
The rear barrel trunnion just slides off the barrel.
The front in contrast is pretty tight.
Here’s a picture of the inside of the front trunnion. The other variant I mentioned has 4 additional rivets that ‘poke’ into the barrel.
They poked like this… but from the inside.
his is how I removed the front barrel trunnion from the barrel. A 2X4 and a hammer. Be prepared to catch the barrel so it does not hit the floor. Of course not sideways.
The next step is to grind the rivets so that hey can be punched out. I had trouble holding them, so I made a holder using a ½ inch bolt and fender washers. You can also just clamp it in a vise.
A look after the rivets are further grinded.
Begin to punch them out.
Close up look.
Repeat for the other trunnion.
Completed front barrel trunnion.
Completed rear barrel trunnion 7 pins
Put the barrel and trunnions away.
Next up is the trigger housing.
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This site was last updated 06/20/09