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Slavia · Moderator

Here comes another project gun: a B3 STEN. My first B3 project turned out nicely, and is now a fun shooter. I'm confident that I can make this one shoot as well, but I want to take the looks of this one in a different direction. The first project:
http://www.airgunhome.com/agforum/viewtopic.php?t=6346&start=0

The STEN was a British WWII era submachine gun. It was used by many countries around the world, and in many variations. What caught my eye was the long magazine sticking out the side - perfect for an underlever airgun. I'm not going for a faithful replica, just something that has identifiable STEN lines. From a discussion in another thread it will be a longer version, with a pistol grip, and the Canadian-style "loop" buttstock. It will be finished with black bedliner. The other thread:
http://www.airgunhome.com/agforum/viewtopic.php?t=9678

I chose the Canadian-style butt because it will be easier and stronger to make with hardware store materials. The pistol grip is to make it easier to handle with a short butt (Alstone says it also helps with muzzle rise on full auto, but that probably doesn't apply). The only place to mount a front pistol grip would be on the cocking lever, which will wobble. I read that paratroopers would sometimes take off the front grip because they would often break on impact with the ground, so I don't feel bad about leaving it off. After all, it's the general lines I'm after. The original design:

I normally just plow into a project, but this time I actually did some planning:

And some "photoshopped" images to look at color schemes:

I have many of the parts roughed out. Note also that this B3 has a one-piece cocking link - my first project had a two-piece articulated version. I shortened the barrel to the length of the cocking arm, which worked well on my first project.

The idea was to simply slip a piece of PVC pipe over the gun and build from there. Some "warts" had to be removed, like the barrel retainer pin. That had to be filed down so the PVC pipe would slide on smoothly.

Some inletting had to be done to get the pipe to fit:

A word about materials - besides the PVC pipe, I am also using plastic salvaged from a discarded store display. I've been hacking on this thing for about 10 years now. It cuts easily, but only by hand. Power tools don't cut; rather they melt their way through the plastic:

The PVC is a different story. It cuts with the Dremel without getting melted blobs. It can be sanded, scraped, or filed. It becomes pliable for bending at the temperature of boiling water. To change the diameter of the PVC pipe all I needed to do was cut a longitudinal slit, heat it in boiling water, and squeeze/stretch it to fit.

Transverse cuts were easy with a hacksaw in a miter box:

Longitudinal cuts were marked by resting the pipe against a three-sided architect's rule. The cut lines were deeply scribed with a pointed knife, and the hacksaw easily followed the scribed line:

More later.

Jeremy · Veteran Member

This looks like a cool project To, I will be watching with interest Cool

I always like the sten gun. Some of them were produced in my town here during the war.

Slavia · Moderator

Got a little more done:

The B3 has three straight pins in the trigger assembly that are only retained by the stock. This particular piece is essential to keep them in place - and also serves as a spacer for the side plates of the "mechanism cover":

Lampy asked if it was going to have a magazine. Of course! It's a requirement. To make it a plausible size for 9mm rounds, I used, well... 9mm rounds. The scraps that I have to work with aren't long enough for a realistic 32 round magazine, so I'll have to settle for 26. It's big enough to hold a small bag of pellets, a loading tool, and a hex key safety device:

Here's the magazine and magazine well:

Nothing on this gun is welded on straight, so straight, level reference lines are scarce. To get the magazine glued on horizontally I think I'll build a jig that uses the cocking lever hanging down as a vertical reference line. Here's how it will look:

I have never done a project with this much plastic (I think now in the 21 st. century they call it "synthetic resin" or "composite material"). Some things I have learned:

1. I am assuming that the store display was jig-built, so I'm planning my construction around factory straight edges and right angle glue joints.

2. A hacksaw gives nice cuts. If you scribe a deep line with the point of a sharp knife, the hacksaw blades follows it. Power tools just melt the plastic instead of cutting it - especially the Dremel with an abrasive cutoff wheel. If you use the Dremel to rough-cut pieces into more managable chunks, wear safety glasses. The Dremel sprays little molten blobs like crazy.

3. Sandpaper will work on plastic, but even better is a file or knife. Scraping a knife blade sideways is reasonably aggressive, and leaves a nice smooth surface. (I'm planning on using bed liner, so a perfect surface isn't necessary.)

4. I have been doing the assembly with super glue. There are products for super-glueing plastic that include a "primer" (just like PVC plumbing needs to be "primed"). I have been wiping the surface prior to glueing with Oops! (similar to Goo-Gone). The solvent goes on a paper towel, not directly on the plastic. A quick wipe seems to clean and soften the surface sufficiently.

More later.

lampy · Veteran Member

Waiting impatiently for the next post...

ZipSnipe · Veteran Member

Oh yeah keep it comin !!

My only problem I have discovered with air guns like this(including mine) is that if ya bring them outside, the SWAT team seems to show up also

Slavia · Moderator

lampy · Veteran Member

Whew! just in time. That should hold me for now. Laughing

I have some spare parts if you need them, I have a couple breech seals and I might have a leather seal. Hell I have a B-3 that you can have for the cost of shipping if you want it.

Slavia · Moderator

I may take you up on that. I have my own brown truck network - the kid is in grad school at Brookings.

lampy · Veteran Member

I'll get some pictures taken and send them to you, if there is anything you are interested in we can work something out.
PM Sent.

Slavia · Moderator

A little more done:

I inletted the magazine well into the reinforcing collar (the second layer of PVC tubing). The magazine latch is from steel pallet strap, screws, and "T" nuts:

I glued and screwed the mechanism cover side plates. I skipped drilling and tapping in favor of simple 6-32 nuts - there's enough clearance for the cocking link, and they won't show on the inside anyway:

I used a gel-type super glue to fill the voids, followed up with a thin bead of JB Weld to reinforce the glue joint. The stamped "U"-shaped channel (that holds the cocking lever) is slightly tapered - the discoloration in the plastic is from heating to bend it straight where it meets the trigger assembly:

More later.

lampy · Veteran Member

Looking good! Thumb Up! v2

Slavia · Moderator

A little more:
I glued in bits of right-angle braces to get as much surface area as possible for the mechanism cover. The compound curve was a challenge. I tried heating to bend it, but when it got pliable it was prone to buckling and wrinkling. I wound up doing it cold, bending it around permanent markers to keep it from kinking:

Closed up and trimmed:

Plenty of clearance for the cocking link:

More later.

Slavia · Moderator

Another installment:

Here's the skeleton buttstock. It's galvanized strap from the hardware store - no jig, just pliers and muscle. The rear loop is soldered together just behind the trigger guard. I laminated the grip from two pieces of fir, cut from a drawer left over from a kitchen remodel. After I made the blank I realized that I was going to put a brass machine screw anchor right on the glue joint, so I doweled it in several places to keep the lamination from separating (actually shish kebab skewers). It will be painted, so the little "dots" don't matter. There is kind of a hodge podge of screw types because I raided the junk box:

Here it is together. The spacer in front of the trigger assembly will need surgery to make the anti-beartrap mechanism work. The grip angle needed to be nearly vertical to allow clearance for my forearm under the stock - STEN's with buttstocks are similar. The stiffener is also something I've seen in photos of STEN's:

It's starting to look like something - every bit as ugly as both the STEN and the B3:

More later.

lampy · Veteran Member

Can't wait to see it in black.

prapor · Member

very good at it. Thumb Up!