Building the Canadian Semi-Auto STEN

[tiriaq]

Stencollector's point about the carbine being muzzle heavy is well taken. I suppose that an option would be to use aluminum rather than steel tubing to reduce the weight a bit. Even the barrel nut and muzzle cap could be turned from aluminum. If the gun were to be given a Suncorite type coating for finish, it would not be apparent that steel was not used.

J. Savoie - I've never seen that video, but I would bet that it describes construction of a smg, not a legal semi auto.

[Claven2]

Other options include fluting the barrel, skeletonizing the bushings, etc.

[stencollector]

Just use a 1-3/8 frostplug with a hole drilled in the center to allow the barrel through it. On mine, I left the barrel a bit larger behind the frostplug. In the case of your barrel, you could weld the fake tube just at the barrel nut end. I usually drill holes in the tube and weld them shut onto the frostplug to hold it in place, but it could also be brazed or soldered into place. Only problem with the soldering/brazing methods is they will not finish the same as the metal.
I had tried a wooden stock on mine to balance it, but it only made the whole affair heavier. It is not so bad with the loopstock.

For the canvas cover, I actually found a roll of the original webbing/canvas. You can also cut up old P-37 largepacks for the material. I did pick up a large blanket of asbestos to use under the cover, but have not used any for possible health reasons. Firing 5 round magazines in semi auto mode really do not heat up the tube that much.

[Claven2]

I was thinking a more aesthetically correct method would be to drill 4 equidistant holes around the tube housing into the barrel nuts and then silver-solder the tube to the nuts and remove any overflow from the seam, then soft-solder some blind dome-head rivets into the holes to help retain the whole affair, like on the originals.

[tiriaq]

Early Mk. II carbines had the barrel seatings sweat soldered (soft solder) and flush rivetted into the casing. Mk. IIIs had the front and back barrel seatings sweated and rivetted with round head drive rivets.
The idea of using a frost plug is excellent. Being pressed from sheet steel, the weight would be minimal.
SOE suppressors used larger diameter tube than the IIS. This results in a very large front end.
If a carbine were registered as non-restricted, a non functional display barrel could be made up for the sake of correct appearance for display purposes.

[Claven2]

Kind of a side-track, but I'm planning on designing a TT-33 magazine adaptor to insert into the Sten mag well and a 7.62x25TT barrel so these stens can be run cheap.

The first step is barrel design. To prove the concept, a 7.62x25TT chamber reamer was fabricated and hardened (not for novices). Buying a reamer is a better idea, but they are not commonly available. Hand-made reamers with 2 blade surfaces clearly don't last like commercial multi-blade reamers do.

The barrel shown WAS a chunk of 2 groove Longbranch No.4 barrel. The base was threaded and a sleeve was screwed on to form the shoulder, then it was pinned in place and finish machined. The next batch of these barrels will be made with take-off 7.65 Argentine Mauser barrels.

[Klunk]

You MADE a reamer???

Now i am impressed

Whats it made of and how was it hardened

come on...no secrets!!

[Claven2]

Fine by me Monsieur Savoie

Klunk, the reamer is made from drill rod stock, you lathe it to SAAMI specification, in effect a dummy round with a pilot guide on the end, than you mill the flats in a mill to make the cutting surfaces.

To harden, it depends on the steel used. You can either casenit it, or use heat and quench cycles on the heat treat chart for that steel.

They don't last like commercial ones, but work OK for a few barrels, and they pretty much require a lathe to keep them cutting straight.

Ok, wrote the above part early this morning when I was in a rush, here's more detail...

The reamer is made out of drill rod. I forget if it is O-1 or W-1. High carbon steel, hardened then drawn slightly. D reamers are a standard type of reamer, not just chambering reamers. Basically, you turn the steel to the diameter or contour desired, and then cut away almost half. A relief is cut on the rounded side up to the edge to create the cutting edge. The edge is finished by stoning. Biggest problem is the risk of warping when the reamer is hardened. O-1 is less subject to warping than W-1. Plunged straight down into the oil or water, not on an angle or horizontal. Doesn't cut as fast as a multi-flute reamer, but if the edge is in good condition, cuts smooth, as can be seen in the photo. Making these reamers is described in older texts. A reamer to size and finish a drilled hole can be made by taking a rod the correct diameter, and cutting it with a long oblique cut. After hardening, the cut face is stoned smooth.

As I said though, it's not a project for a beginner as there is a high probability of making a mistake and ruining your barrel blank.

[Claven2]

DISCLAIMER: Stencollector has been kind enough to allow me to post and use his collection of material on building his SAS3 Sten, the actual gun used to get RCMP approval. The following is his work.

The mag well collar is manufactured it from 1/8" plate. Photo one shows the plate being bent around. The mandrel being used is an old roadwheel pin from a Brengun carrier, turned down to the outside diameter of the tube. The next photo shows it bent completely and before having the seam welded. The origionals were approx .105 thickness, although this varied between manufacturers. In another photo you can see where the outside of the tube is being turned to the correct thickness. The inside had to be bored slightly to provide a nice (but not loose) fit. The last photo shows the ejector port cut into it.

The port was accidently cut too long...had to weld a little metal back in place. The locator pin has already been drilled, and the magazine opening roughed into place.

[Claven2]

DISCLAIMER: Stencollector has been kind enough to allow me to post and use his collection of material on building his SAS3 Sten, the actual gun used to get RCMP approval. The following is his work.

Again, 1/8 sheetmetal was used. A mandrel the size of the internal magwell was made up and used to make the bends. Once the holes were cut for the mag release, and the front slot for the housing release, this piece was located and welded on to the tube that was made in the previous post. It was initially tacked it into position, then assembled onto the receiver to make sure that the gun would feed.

At first, the last round would continuosly jam. For whatever reason, the housing prefferred to be further back than on an original sten, so the welds were cut and the mag box was moved further back. The triangular bent barrel nut lock had to be custom made since this dimension has been changed by the repositioning of the housing. The last photos show the stamping of the markings on the housing.

This housing is stamped with the serial number 0S04. The serial was alsostamped onto to the tube and the trigger housing, since Stencollector was concerned that the ruling about what constitutes the receiver could one day change.