Building the Canadian Semi-Auto STEN

[Claven2]

Hmm... what could this parcel be!?! It seems to have come from the States...?



Let's see what's inside, shall we?



Looks like my two SAS3 kits have finally arrived!



And to top it all off, they even come with the latest revision hammers!



Looks like we'll be making some build progress soon - stay tuned!

[J. Savoie]

Now, I need all the details please:
-Where did you get it from? Semiautosten.com I imagine.
-How much (total including postage, taxes and duty please)
-Did it take long long before you got it? (from the moment you sent your $ until you got the delivery)
-Did you need any particular papers to import it?

Oh boy! Oh boy! Oh boy! Don't let us wait too long please!

J. Savoie

[Claven2]

Now, I need all the details please:
-Where did you get it from? Semiautosten.com I imagine.
-How much (total including postage, taxes and duty please)
-Did it take long long before you got it? (from the moment you sent your $ until you got the delivery)
-Did you need any particular papers to import it?

Oh boy! Oh boy! Oh boy! Don't let us wait too long please!

J. Savoie

1) Yes, Semiautosten.com
2) $569.15 USD for the two kits and shipping, not including any duty charges.
3) The kits were delivered 2 weeks to the day after semiautosten.com received payment - from Canadians they take only money orders mailed to them, and drawn on a US bank.
4) I didn't import the kits, so I cannot comment on the mechanics of that. I bought the kits here in Canada, someone else imported them for me.

The machining of these kits seems pretty straightforward, actually. It MAY be possible to devise a Canadian offering. We shall see.

In case you did not know, the photo of the template is actually the receiver tube. The templates come pre-adhered to the metal receiver tubes.

[stencollector]

I am sure you guys will figure these things out, but I'll add a quick blurb on what changes have to be made to convert the mk3 template to mk2 conversion.
Of course, you will cut the tube to the shorter length, and square the end off in a lathe. Then you will have to turn the inside diameter of the tube the appropriate distance to fit the trunnion in. I found the next hole to make was to match up a hole with the magwell release pin. Then from there I cut the openings to match my magwell ejection and magazine ports. The ejection port should be the same as is on the template.

One other change you are going to have to make (besides the front sight dovetail of course) is to position the ejector in relation to the bolt. You will find that the mk2 style of ejector will interfere with the bolt, so you will have to groove the bolt slightly where it wants to hit the ejector. To be able to use the safety slot, you will have to remove a bit more metal on the bolt to allow it to turn and miss the ejector. I would also suggest welding the ejector in as far as it can go against the slot in the bolt. Mine has to be cut out and repositioned....I currently end up with the occasional spent case stuck in the tube.

Someone mentioned that, on the curent produced kits, the guide rods which hold the springs aren't threaded to go into that end cap. Are yours?

[Claven2]

The newer kits have a shorter slug, shorter hammer, and longer (better) springs. The rods are not threaded as the new design specifies they be welded to the slug.

Should be interesting to see if Spencer gets to keep his new open bolt effort. If so, the original sten design is easier and cheaper to scratch build if you have a mill (check) and lathe (check).

For now I'll proceed with SAS3 guns and possibly try another later using open-bolt, but of course will scratch-built the receiver and possibly the bolt too.

[stencollector]

That makes sense on the shorter slug and longer springs. I was actually going to recess my springs into the bolt and hammer to get more room for longer ones. The ones I have now have held up OK to a split between IVI and commercial ammo, but I would prefer longer.

After my experience with the CFC, I wouldn't bet on a decision on the open bolt any time soon. It would be nice if there was, I too would go that route. But I suspect there will be a few obstacles and roadblocks thrown his way yet.

[Claven2]

Let's talk about casings for dummy silencers.

The casing for the 18 3/4" barrel has now been made. This isn't made from high-end DOM tubing, its just galvanized EMT stock with the zinc removed. Actually this is thinner and lighter than DOM, so its better for this purpose. Centering plugs were made so that SAS sized tube can be supported against the tailstock while the steady rest is adjusted. This diameter tube cannot fit through the lathe spindle being used, so we have to use the steady rest to bore out the tube to accept the barrel seating. Where the spot welds were, the steel is hardened which makes turning in the lathe difficult. It's easier to adjust the tube than the seating for this reason. The tube for the housing collars is smaller than the casing inside, and larger outside.

This is done deliberately, so we can get a better fit, boring and turning, rather than trying to use a stock size, and hoping that it works.

Some housing boxes have been made, one using two L shaped pieces, seams along opposite corners, the other a U shape, with a separate back welded in. The above jig was used and since there is no weld shrinkage, these aren't going to require any filing along the inside to get the best magazine fit.

[Claven2]

Here, a SAS3 bolt (extreme left) is compared with two newly shop-made experimental (machined to be semi-auto only) open-bolt STEN bolts, one patterned after a Sten bolt using basic dimensions available on line (middle), the other reconfigured for a bottom feed MP3008 style (far right). Note that the sear engagement surfaces extend all the way across the bolts, for semi auto only function (ie, no matter what position the selector is in, the interruptor would be tripped). It is unknown if either of these open bolts actually function, there being no real Sten or MP3008 in my posession which to test them, but from an engineering standpoint, they would run just fine.

If an open-bolt gun is approved, machining semi-only open bolts looks to be no big deal. The SAS bolt is a more difficult endeavor, but may still be doable in the advanced home shop.



Here are some more views:

[Claven2]

A SAS3 Sten uses tubing with an OD of 1.500", and a wall thickness of about 3/32" or .093" to prevent an original bolt from being inserted into the tube.

The original Sten recoil spring guide and barrel block won't fit, as a result. It is necessary to alter either the tube, or the parts - the tubes that come with the kits are relieved inside the rear of the tube for the spring guide, but NOT for the barrel block as the kits are meant for MkIII repros, not MkII's.

Because this lathe (a 13x40 Standard Modern) will not pass a 1.5" diameter piece through the spindle, so the steady rest is used to allow the ends of the tube to be bored out.

An aluminum plug with a centered hole was made which is a tight fit in the tube. One end of the tube is mounted in the chuck, the other end is supported by the tailstock centre. The steady rest jaws are then adjusted against the tube. Once adjusted, the centering plug is knocked out, and the boring bar is then used to bore out the tube enough to clear the barrel block and spring guide.






See kids - shop class WAS useful!

Here is the SAS3 bolt with a reproduction MkII cocking handle fitted.




Here is the blank tube and a template. The template is bonded to the tube, and then the openings are milled out. An alternative would be to coat the tube with machinst's blue, and scribe the lines onto the tube.



The SAS3 kit comes with a template already bonded on, but it is a MkIII tamplate. It is sometimes easier to start with a new template made from STEN drawings than to bother modding the SAS3 template.

[NavyShooter]

FRT Report
webFRT v2.07

Firearm Reference No 126844

Summary

Make: Homemade
Model: Sten MARK 2 Copy
Manufacturer: (Blank)
Level: Non-Commercial Customization
Type: Commercial Version
Action: Semi-Automatic
Country of Manufactuer: (Blank)
Serial Numbering: Numbered
Legal Classification: Restricted

Caliber, Shots and Barrel Length
Firearm Ref No: 126844-1
Caliber: 9mm LUGER
Shots: 5
Barrel (mm): 197
Legal Classification: Restricted
Legal Authority: CC 84(1) "Restricted Firearm" para. (b)
Level: Non-Commercial Customization
Barrel Type Code: (Blank)

Notes

Make
-Make is not found on the firearm.

Model
-"SAS-3 MK 2", "T-15 IND", "CANADA" and a serial number is marked on the magazine housing of the firearm.
-this firearm is a homemade semi-automatic only reproduction of a Second World War STEN MARK 2 submachine gun, distinguished by its all-metal welded construction.
-the basis of this fabrication is the SAS-3 (Semiautomatic Sten Mark 3) tube kit as sold by T-15 industries, salvaged scrap parts, and a homemade magazine housing; deemed to be the receiver/frame.
-features include: fixed open sights; a "wire loop frame" style stock; tubular construction; 7 3/4" / 197mm barrel, and magazine housing that extends to the left of the receiver tube, an AR-15 type firing pin and a specially manufactured bolt assembly from T-15 Industries.

Action
-closed-bolt, striker fired, blowback operated.

Serial Number
-observed serial number was located on the magazine housing.
-the observed serial number consisted of a number followed by a letter followed by two digits.

Shots
-detachable box magazine.

Canadian Law Comments
-this firearm has a homemade receiver/frame which, in conjuntion with SAS parts, supports only semi-automatic fire.

Cross-References
No Data Retrieved

Also Known As/Product Code
No Data Retrieved

Year Dates
No Data Retrieved

Importer
No Data Retrieved