I like the 32 round Sten mags but darn are they long!

Had anybody cut one in half and figured out a way to bend a lip for the floorplate to grab onto?

I'd like a shorter mag for prone, seated, and shooting off of the bench.

411?

I have the same problem -- trying to sight the rifle in off a rest with a 32 round sten mag in it so I did the above short 10 round mag. Their soft steel so it's no problem. The most time is spent duplicating the flang on the bottom.

nice job,  was thinking of doing the same thing to my Oly 40 cal. I have some magazines that feed like crap so no big loss if I screw it up.you never hear of people wanting smaller magazines, i'm scared.

Looks great!

So I could take my Rotozip saw and put on the metal cutting wheel and cut the mag tube in half?

Then how did you bend the flange for the floorplate to grab onto?

I'll assume you took it to the range with some HD wire cutters and adjusted spring tension there.

Am I missing anything?

Just can't see paying $50 for a mag block and another $65 plus postage for Oly to then as for customer-supplied Glock mags and pay an additional $5 per mag.

Could just spend $25 and get a bag of Sten mags and cut up a couple.

Anybody with know-how please chime in.

An UN-informed question might be "Is the modification creating an illegal magazine?"

Logic says NO but...

Didn't Oly have some Simmunitions mags that fed the 9mm? They looked like regular AR mags or something.

Ah heck, I don't remember anymore :-)

Quoted: An UN-informed question might be "Is the modification creating an illegal magazine?" Logic says NO but...

I was thinking the same thing, if the shortened magazine wasn't 10 rounds or less in capacity, couldn't it be considered creating a 'new' high capacity magazine??? Sounds ridiculous, but I wonder....

I had the same thought about shortening Sten mags.  Not for bench shooting, jsut to fit the leather Swedish mag pouch I have.  The Sten mags are about 2" too long.  When comparing my mags (TAPCO 10-fer deal) I've noticed 1 that is about 3/4" longer than the others.  Fit & finish is'nt as nice as the others either.  Possible village blacksmith knock-off?

Quoted: Quoted: An UN-informed question might be "Is the modification creating an illegal magazine?" Logic says NO but... I was thinking the same thing, if the shortened magazine wasn't 10 rounds or less in capacity, couldn't it be considered creating a 'new' high capacity magazine??? Sounds ridiculous, but I wonder....

It's legal to modify a pre-ban magazine to hold more or fewer rounds than it already does.  The limits on modifications are that you can't use post-ban mags to extend the capacity of an existing pre-ban mags (so no welding a pre-ban and a post-ban together to make a bigger mag) and the magazine must still fit the weapon for which it was designed, if it's being modified to also fit another firearm.

No, I don't know how Olympic gets away with modifying sten mags like they do without getting hassled by the ATF.

I built the mag for the same reason that duncan mentioned -- to be able to sight the 9mm AR off a bench rest. I was under the impression that any major change to a pre-ban magazine would automatically make it a post-ban mag and it would fall into the 10 rounds or less category.
I now think, and I could very well be wrong but, if the mag is the same or less capacity and still works in the firearm that is was intended for, it should be legal. I figured better safe than sorry so I made sure it was only 10 rounds anyway (I don't know if this is California legal). I only needed it for sighting in the rifle at the outdoor range. After cutting the mag body down to a size that would also allow for the extra metal for the rim on either side, I cut out the front and back part of the base with a Dremel, put one side of the mag body in a vise and bent the mag over 90 degrees. I did the same thing on the other side of the mag so now I had two good sized flaps sticking out of the mag base. I ground them down slowly till they were the same size as the originals. My final length on the spring is 6 and 1/2" long and it seems to work just fine but I noticed that some sten mag springs are shorter than others so they may be fatigued so be careful, best to cut your spring a little long to start with.

Funny -- I thought I was the only one that needed a low-cap mag!

Thanks for sharing!

Just ordered the TAPCO 10 Sten mags and a Danish carry sack both for $24.99.  

They usually sell those separately for $7.99.  Really nice deal.

Can always use the sack for when you load up 6-10 32-round Sten mags.  Those mags get heavy when fully loaded!  Better than weighting down your tactical rifle case with other gear.

Hopefully I get a good seven/eight clean mags out of that deal.

And then I'll have several "short" Stens!

AR-fan,

Man, I don't check the board for a few days and this is what I find out?!!!  Cool.  I was thinking of doing the same.

Did that hi cap Sten mag show yet?  The Lancaster????

Edit-I'm gonna post a link in the Sten Block topic to this..... don't want it to get lost...

Quoted: (SNIP, SNIP) It's legal to modify a pre-ban magazine to hold more or fewer rounds than it already does.  The limits on modifications are that you can't use post-ban mags to extend the capacity of an existing pre-ban mags (so no welding a pre-ban and a post-ban together to make a bigger mag) and the magazine must still fit the weapon for which it was designed, if it's being modified to also fit another firearm. No, I don't know how Olympic gets away with modifying sten mags like they do without getting hassled by the ATF.

Circuits (and anyone else),

So, in theory, if one were to shorten one Sten mag- you have this section of tube from a pre ban mag.  And being a good person, one doesn't want to waist things..... So, one could "weld" it to another Sten mag to make a larger capacity mag?  Using your example, one is 're-using' preban mag material....

Both are "pre ban".  And both will still work in the weapon it was built for.

Okay, lining it up to weld for the average 'joe' maybe a problem, but that's a whole different issue.

Edit- Well, I recall that I've seen so called pre ban 223 mags that were modifed to 10 or 5 rounders before.  Those were legal.  Why wouldn't this be?  What, the anti's have a problem with lower capacity hi cap mags????  Or they gonna moan that it's easier to hide..... (sorry... ranting.)

Kaliburz,
   The Lanchester hasn't gotten here yet (Darn).
You know, it's funny --I was thinking about what you just said about welding the pieces together --
FRANKENSTEN,
THE 500 ROUND MAG FROM THE GRAVE!

Still waiting for those TAPCO Sten mags to come.

In the meantime, what did you use to grind down the mag flanges so the floorplates would work.

Was thinking about buying a $40 bench grinder.

But what about the ole flat file most of us have.  Couple passes should make it fit?

I shortened the flanges, after they were bent, two ways. In each case it is most important to compare the new flange to the original one when you get close to the final size.
The first was to hold the flange next to the side of a grind stone and cool it every couple of seconds in water. When the size was starting to get close I would have to clean-up the top and bottom of the edge with a file because the metal melts as you grind it and kind of rolls over the sides. Final fit is with a file.
The second way was faster -- mark a line about 1/8th " out with a scrib or felt pen and use a dremel to cut the flange then use the side of a grind stone and file to do the finish up work. If some of the flang gets screwed up its ok as long as ther is about 2/3's of it for the end cap to slide on to and the end cap covers a lot of mistakes!
after you've done a mag or two you may find your own way to make the flange.
By the way, I wasn't sure exactly were to make the first cut to shorten the mag so I took the end cap and spring out of the original mag and used something to hold the follower as I put the amount or rounds I wanted in the mag PLEASE REMEMBER TO ADD ONE ROUND MORE THAN YOU WANTbecause, in my case, the mag presses up against the bottom of the bolt and if the ammo is topped off there isn't any play and the mag can't even be forced in.
Now hold the mag up-side-down with the ammo and follower in it and measure down the inside of the front of the mag till you hit the edge of that front leg of the follower. Subtract an full inch from that measurement. Now empty the mag and use that final measurement to measure on the outside of the mag front from the bottom, and mark this on the mag. I cut a piece of paper and put a bit of scotch tape on one end and rapped it around the mag with the top edge just below the mark. If you line up the upper edge of the paper strip with itself and it is fairly tight all the way around you can use this to draw a line all the way around the mag that is darn close to straight and perpendicular to all the mag edges. Cut the mag in half at this line. Make a new line by marking the mag one inch up form the new mag bottom and use the piece of paper to help draw another line around the mag. This is the final mag length. Use a dremel to cut down just to that line on all four corners. Now use the dremel to cut out the section of the front and rear of the mag as shown in that first picture I posted. The mag flanges are ready to bend -- put one flange in a vise and as you close the vise adjust the line you drew on the mag so it is straight across the top edge of the vise and bend the mag down 90 degrees like in the second picture. Do the same on the other flange and they are now ready to be cut and sized. You may find, because of the length of the flanges that they are hard to put in the vise on that first bend -- just kind of force the mag in the vise the other flange will get bent slightly but your going to fix that shortly.

Thanks for taking the time to share the details!

Use a Dremel with those thin metal cutting disks or a Rotozip with a metal cutting wheel?

Was thinking of mounting uncut mag on miter saw frame and clamping it for the "big" cut.

More process please?

Duncan,
   I'm sorry but I'm not familiar with the rotozip but I'm am with the dremel. The cutting wheel I use is the reinforced cutoff wheels #426A -- they are stronger, larger and last longer. I did the main cut with a portaband, a hand held band saw for metal. a hacksaw will do the same for cutting the mag body in half, the rest of the work I did with the dremel, file and the grindstone. If you have a miter box that will work with a hacksaw great -- it should make a nice straight cut.

AR-Fan et al:

Just wanted you to know that it turned out great!

I have five Sten mags that are now 15-rounders that are half the size of the originals.  Easier bench and prone shooting.  Wish I had a digital camera to share.

Anyway, you can use the metal blade/saw attachment on the Rotozip to carefully cut the mag body.  

And as you stated, I also used a Dremel with several cutoff wheels to cut the notches out of the fronts and rears for the flanges.

I bent the flanges with a regular ole vicegrip and filed till the floorplate fit on.

Took about 18 minutes per mag once I finished the first one.

BTW - out of the 10 Sten mags and haversack deal from Tapco, 9 were in acceptable shape.  One was pretty rusted and pitted, but I still think it will function - just ugly.

I also used a thin coat of Tetra gun grease on the runners and outside of the mag followers and see some improvement in smoothness.  I just wipe off the excess in time.
Thanks for the inspiration and the tips.  They worked!

Duncan,
   Glad to see you nailed it. It's nice to know that you can now have just the size mag you need and if one gets screwed up -- no great loss. Even the cheap uzi mags I get cost $11 bucks a piece so I don't even think about cutting one of them.

AR-fan, what is your source for Uzi mags?

Quoted: Didn't Oly have some Simmunitions mags that fed the 9mm? They looked like regular AR mags or something.

Oly does have "special" simunition mags for their simunition upper.

They are plastic and have a blue bottom.

FYI: The Oly simunition upper has a great patented safety feature that does not allow "real" 9mm to leave the barrel.  Much like a gas relief overpressure valve.  You shoot real 9mm, all gas goes out special pressure tube...

Boom_Stick,
    I got used 25 round mags from DSA at http://www.dsarms.com
I'm not sure if you would care for the smaller package but they cost $10.95 each. I bought a bunch of them plus I have some 32 round Colts but right now I'm using the 32 round Stens with my modified magwell kit.