STEN Mk III Semi-auto Build Project - 1ST TEST @ the range

1st time I took my home built STEN Mk III. I finished it the weekend before and refinished (Parkerized and painted) the STEN the night before the range test.

I fired about 250+ rds through the STEN. For the most part it was pretty reliable. It's a brand new carbine, so it has to be broken in and a few things tweaked. I had a few very minor issues that I was able to correct on the spot. There are a few more tweaks I'd like to do to get it to be 100% reliable.

I'm pleasantly pleased with the STEN build, it was easier to make then I was led out to believe. I have experience building other types of firearms.

STEN Mk III semi-auto 9mm carbine Build Project.

This is a legal semi-auto build and an approved STEN design by the ATF. The STEN was built to comply with both Federal and State firearms laws.

STEN Mk III parts kit looks to have been built originally in the 1st half of 1944 according to the serial #. It's a Finnish Army model (stamped "[SA]"), which included a sling swivel under the receiver and on the stock.

The reduced diameter STEN tube will not accept the original STEN FA Open Bolt. The unfinished STEN tube, semi-auto bolt, 16" barrel, a recoil assembly is from Indianapolis Ordnance.

Most of the drilling and machining was done on an old 1hp Rockwell drill press. I purchased a cross slide table (X & Y axis) and a vise. Used some center point drill bits and a couple end mills. Dremel, angle die grinder, cut-off tool, aircraft rivet gun, hand files.

Special features:
Removable barrel and front trunnion.
Lower receiver lug, allow the complete removal of the trigger group.

Finish:
Parts blasted with aluminum oxide, then Parkerized with Manganese phosphate solution, and painted with Dupli-Color Engine Enamel semi-gloss black (#DE1635).

Category:

Sports

Tags:

• subgun
• carbine
• 9mm
• Mk
• II
• WWII
• Mk3
• Mk2
• Sterling
• ca;guns.net
• cgn

[MrSTUART01010]

How did you attach the barrel

[REDHORSECA]

@MrSTUART01010

The barrel just fits between the rear and front barrel trunnions. The barrel trunnions are riveted to the receiver. The way the barrel is turned, it just sits between the trunnions and it does not move fore or aft.

[tuchicilina]

you don't hold it like that!

[REDHORSECA]

@tuchicilina I don't know whom you're talking about. I was test firing in the beginning, I wasn't about to put my face near the receiver until I had fired a few test shots. My buddy shooting at the end, there was a problem with the mag. One side of the mag feedlips was dragging on the bolt. We had to twist the mag in the magwell so it wouldn't drag on the bolt. The mag was probably 50-60+ yrs old, not in the best of shape. Mag feedlips was latter adjusted. He was shooting it great like that.

[duffman0286]

I just bought my kit and getting ready to build mine but that kink of the bolt slamming the rear barrel trunnion kinda worries me a bit. how can you correct it or is it something you have to life with?

[REDHORSECA]

@duffman0286 That is simply the way most blowback carbines/SMG operate. Completely normal for the bolt to slam against a trunnion/barrel. The STEN SMG does this in full auto, so I don't think there is anything to worry about in a semi-auto. Just make sure to inspect the rivets for the trunnions from come loose. The factory STEN SMG from WWII also silver brazed the trunnions to the tube body, along with the rivets.

[jkiser991]

isit legal t build one semi auto? i just contacted atf and this guy said no so i have teparts kit already can someone let meknow?

[Allmightylulala]

Hi, usually the sten gun fires with an open bolt. How is it that your sten fires with the bolt closed? What's the difference?

[mark16443]

does the bolt slamming on the trunnion hurt it at all? i think im going to build one only with the vertical mag kit instead of side mag. do they only take sten mags or can you use the mac 10 mags in it too?

[poopfist]

Nice build!



[xgi36]

Thanks for the info I have a kit stored somewhere just waiting for "how to do it legal"

[deadgoodman]

nice! MacGyver

[tuchicilina]

@REDHORSECA oh, sorry to hear that, but all i know is that if toy hold it like that it would not feed properly, but i'm glad you fixed it. btw, how much time you spent making it?