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Alternate magazines for UD42


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#1 DUBLBZ

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Posted 21 June 2020 - 01:23 AM

The UD42 magazine is different from all other 9MM magazines because when it was designed to supplement the U.S. military Thompson submachine gun, the designer wisely chose to use the same magazine as the TSMG used (although that may have been required by the military). The original design was provided for testing in 45 ACP caliber, using the same magazines, which were abundantly available and totally reliable. The ammunition supply chain would not require anything new.

When the .45 weapon was not selected for U.S. use, alternate users were in need of 9MM weapons. The design and tooling was already established for use of that style magazine (utilizing a "T"-spine for mounting to the weapon). Converting to 9mm would only require some small changes to the weapon if they left the same design for mounting the magazine. Manufacturing them in 9mm was also not  a problem for the many manufacturers of the TSMG magazines.

If a UD42 and a TSMG magazine are placed side by side, "T"-spine up, one sees that the mounting is absolutely identical.

I am currently experimenting with creating an alternate magazine when OEM UD42 mags are not available, or maybe more than just 20 rounds are desired. The combining of a 30 round TSMG mag outer housing and a UZI 32 round mag (one I had at hand to compare) pushed up inside will do the trick. Another that may also work is a ASC Colt style made for AR15s in 9mm. 20 or 32 round versions are available. The four insertion limit protrusions on the UZI mag need removal (not so with the ASC mags). The top of the TSMG 45 mag has to have some of the feed lips removed to clear the access into the UD42 receiver in order to latch up. A later post will provide pictures and dimensions. A little more off the bottom to match the lengths and allow access to the base plate of the UZI mag. If done judiciously, the finished project, when mounted to the gun, should be almost indistinguishable from an OEM mag, other than a little longer and a touch fatter. A 20 round ASC mag coupled with a 20 round TSMG mag housing would look a lot closer to a UD42 OEM mag. Only experts will know the difference.


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#2 Dingo

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Posted 21 June 2020 - 06:52 PM

The original UD42 magazines are 25 round, not 20


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#3 APEXgunparts

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Posted 22 June 2020 - 02:43 PM

The original UD42 magazines are 25 round, not 20


OOPS!
Looks like I need to change the wording on the UD-42 magazines that APEX has for sale.
I don't have live ammo in the shop to check such details.
I am not sure why the double mags we have were separated at some point.

Richard


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#4 APEXgunparts

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Posted 22 June 2020 - 02:57 PM

I just looked up the UD-42 in NELSON's book "The World's Submachine Guns, Vol. 1"
In the text it describes the UD-42 as having 20 round capacity magazines with the dual mags being 40 rounds.

I looked in that book as the info I found on-line was conflicting, some sources say 20 and others said 25 rounds.

Richard


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#5 StrangeRanger

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Posted 22 June 2020 - 04:36 PM

All my references also say 20


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#6 DUBLBZ

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Posted 22 June 2020 - 08:12 PM

I can only get 20 in mine. Does that take precedent over some obscure documentation?


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#7 Dingo

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Posted 23 June 2020 - 05:28 PM

I have had 2 UD s and many magazines, all mags was 25 rounds. Lots of books and videos have it wrong. Check You Tube video: VSO Gun Chanel , MP40 VS UD42


Edited by Dingo, 23 June 2020 - 05:46 PM.

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#8 DUBLBZ

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Posted 24 June 2020 - 02:22 AM

My apologies to Dingo and a comment to Apex.

Full disclosure - I'm pushing 80 and have had my '42 since 1957. Haven't fired it in a lot of years as other things got in the way.

My memory is not what it used to be, so I decided to double check. Dingo is correct. I successfully got 25 rounds in a mag (as indicated at the last "count" viewing hole). It looks like a lot of documentation out there is incorrect

I looked at the APEX site, found the UD42 mag for sale and took a good look. If the comment about separating a double-mag refers to the picture on their site, it has NOT been separated from another. The double-mags have two small spot welds at each end (4 total) on the front where the ID stamping is. That side of the mag looks perfect - no sign of spot weld separation; it would ruin the mag.

Have pictures but can't find my USB cable for the camera, and wouldn't you know it - The FUJI doesn't take a Micro-USB, something called a mini 8-pin. Need to find one.


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#9 APEXgunparts

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Posted 24 June 2020 - 10:38 AM

My apologies to Dingo and a comment to Apex.

Full disclosure - I'm pushing 80 and have had my '42 since 1957. Haven't fired it in a lot of years as other things got in the way.

My memory is not what it used to be, so I decided to double check. Dingo is correct. I successfully got 25 rounds in a mag (as indicated at the last "count" viewing hole). It looks like a lot of documentation out there is incorrect

I looked at the APEX site, found the UD42 mag for sale and took a good look. If the comment about separating a double-mag refers to the picture on their site, it has NOT been separated from another. The double-mags have two small spot welds at each end (4 total) on the front where the ID stamping is. That side of the mag looks perfect - no sign of spot weld separation; it would ruin the mag.

Have pictures but can't find my USB cable for the camera, and wouldn't you know it - The FUJI doesn't take a Micro-USB, something called a mini 8-pin. Need to find one.


Surprising empirical info on the mag capacity.
NELSON's book is supposed to be the "GO TO" book on SMG's!
I have our "fair" condition UD-42 magazines listed.
I have not yet listed the other "good" condition magazines or the separated pairs.
I will try and get those posted on the site today.

Richard


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#10 DUBLBZ

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Posted 24 June 2020 - 03:02 PM

Looked at the "Separated" magazines at APEX and was surprised at the good useable condition. Not ruined like I thought they would be. Don't know why somebody would do that as there were far fewer "doubles" than single mags distributed, thus more valuable. The remnants of the spot welds look exactly like those positions on mine.


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#11 APEXgunparts

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Posted 24 June 2020 - 03:43 PM

Looked at the "Separated" magazines at APEX and was surprised at the good useable condition. Not ruined like I thought they would be. Don't know why somebody would do that as there were far fewer "doubles" than single mags distributed, thus more valuable. The remnants of the spot welds look exactly like those positions on mine.


These UD M42 magazines came out of the material that was part of the purchase of the contents of Springfield Sporter's warehouses.
There are a few "mystery's" that have come to the light of day, separating those magazines is just one of them!

You have owned your UD M42 for a bit longer than I have been alive!
Do you know any of its prior history?
I have seen a few of these guns as demilled kits, and they all looked like they came from some small country with a hot humid climate!
They are a neat SMG, I think I have only ever seen one in person.

Richard


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#12 DUBLBZ

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Posted 24 June 2020 - 05:19 PM

APEX -

It started life with me as a demil at Hy Hunter's American Weapons Corp. in Burbank, CA. Check out the 1957 Machine Guns Collectors List #3, available at Cornell Publications. "Special Offer" in it got my attention. I had an original catalog, but lost it along the way.

Came with a single mag, as pictured. I picked up another plus a double with an original case for it at gun shows in subsequent years.

I love the "junk pile" tables. Never know what you will see for cheap prices.

Serial number is in mid 14ks. If the numbering system started at 00001, that would put mine at the very end of production if the 15k total production numbers are accurate. It was and still is in very good condition. No rust or scratches. Evidence of very little shooting. The demil was expertly done with almost no external sign of it being done. Welded between chamber and mag.

Went to buy a Thompson, but couldn't resist this when I saw it.

Pictures to follow when I get a another USB cord for my camera.


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#13 Dingo

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Posted 24 June 2020 - 05:39 PM

Some of the UD42 s ended up in Indochina and Philippine , that might explain why they looks like they came from a humid climate. Those we have in Europe was usually dropped in places like Netherland, Crete, France and Norway and they are normally in god shape.


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#14 DUBLBZ

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Posted 25 June 2020 - 01:26 AM

I need to correct one word used in the description of my '42's history with me. "Demil" was used, which is appropriate for all recent NFA stuff, but back in those days the term was DEWAT, which stood for deactivated war trophy. A big difference in resulting parts & assemblies.


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#15 MG08

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Posted 25 June 2020 - 05:15 PM

I have a UD 42, and a pile of excellent mags from back in the "old days"  when this stuff would show up. Still, I would be interested in seeing plans to make the OPs described magazines - just for grins.  And no, I am not interested in selling either the SMG or mags at this time.


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#16 DUBLBZ

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Posted 29 June 2020 - 01:00 AM

Finally able to get pictures. Making a little, slow, progress on converting a TSMG/UZI combo mag for use in a UD-42. The modification of the top, feed lips end of the TSMG mag is finished to allow lock-up in the '42. Looks and fits good. The lips were ground down on a disc sander by .37 inches (started at 1.20" from top of "T"-spine to top of lips, down to .83" from top of "T"), keeping the surfaces parallel and 90 degrees to the body. The front small lip, which is straight across in the middle, had to be ground down into a radius matching the receiver, since it is outside the machined mag recess. Pictures attached.

I have a small concern with the UZI mags. During a little research into 9mm AR-15 configurations, some comments by owners of the Colt SMG magwell conversions which used modified UZI or ASC Colt SMG magazines stated they had had some FTF during the last few rounds. The bodies and followers of both seem to be identical. The bodies have almost no taper from front to back; way less than the '42 OEM mags. A significant tilt to the follower seems to be a compromise to account for the differences in 9mm ammo taper when stacked in a mag body with no or little taper. Sten and Suomi mags have higher body taper like the OEM '42 mags along with a follower that is parallel with the feed lips at the top. UZI and ASC Colt mags have significant tilt between follower and feed lips at the top, maybe contributing to the FTF in the AR-15 configurations. UZI or ASC Colt mag pushed up into a TSMG mag is simpler because of their smooth outer bodies. Sten or Suomi would be preferred if not for all the outer steel welded to the bodies that would have to be removed. Way too much work.

I also decided to change the modification at the bottom. Instead of removing about 3/4" off the TSMG mag, allowing no change required to the UZI mag, I am removing the bottom plate retaining sheet metal on the UZI mag and leaving the base plate on the TSMG mag. The spring will be a little longer in both relaxed and compressed modes, or a light spacer could be used if spring tension is too little. It will look so much better.

Side note - OEM '42 and TSMG mag has .030" thick body walls and the UZI has 1mm (.040") thick walls. Don't have others to measure.

More after UZI mag inserted.

 

Attached Files


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#17 DUBLBZ

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Posted 06 July 2020 - 07:03 PM

Finished the converted magazine. A few comments on things learned doing this.

1 - Thompson 20 round mags and M42 25 round mags are identical except for the back to front body taper, and very slightly smaller front to back and side to side, accounting for 9mm ammo dimensional differences from 45 ACP. The confusion as to whether the M42 mags hold 20 or 25 may be due to the absolutely identical round-count witness holes as the 20 rounders for Thompson have. Looking at them sideways, one is hard-pressed to tell them apart. My OEM '42 mag is the hard-chrome plated one. 4 holes at 5 rounds each don't really count 25 in most peoples minds. Who knows why the holes didn't get in the proper position, plus one more, when the M42 mags were manufactured. Probably not worth changing the punch press set-up. See pictures.

2 - Don't use a UZI mag. Use a Colt style SMG 9mm mag. Grinding the insertion limit tabs off the sides of the UZI's is way too much work. Hardened thicker steel took a lot of effort to remove with a Dremel. I was surprised at how hard the steel is; but doesn't get bent when dropped.

3 - The top of the feed lips must be ground down very slightly to be absolutely 90 degrees to the length of the mag as shown in attached pic. Not doing so will not allow the bolt to pick up cartridges. The top of the feed lips have to contact the machined ledges on each side, where the ejector is pinned, at the top of the mag well. The back is key.

4 - During my insertion process, which started at the bottom of the Thompson, the fit was tight enough that I used my shop press to start it. Nearing the top it essentially fell in. maybe starting at the top is a better option (by hand). It is almost an exact fit, with line contacts at each front corner radius and the back. No lubrication is necessary; de-greasing is. I used automotive brake cleaner on both mags. Other than the back, there is a little space between each magazine at the front and both sides. it is not much; I didn't "feeler gage" it. If the fit is too loose to stay in position after having it push down during "latch-up" (touching the machined ledge mentioned earlier), slightly bending the top of the two sides of the rear wall inward will create just enough pressure to hold it. ****NOTE - during first attempts, the front edge of the UZI mag just barely contacted the front of the machined mag recess in the receiver, thus pushing it down into the mag about a 10th of an inch, away from contacting the aforementioned ledges. The position of the UZI mag is just a little forward of where the OEM mag is positioned (about .040" or 1mm at the back plus another .010" difference between thickness of mags at the front). A choice needs to be made as to remove a very little at the front edge of the receiver recess (Sacrilege, I know), or remove some at the top front of the UZI mag until it just clears and doesn't get pushed down during latch-up.

5 - Retaining the inner mag in position became the next issue. I decided to use "Gorilla Glue" as it holds well after expanding a little and is not brittle after "Set". This filled the slight spaces between the two mags. Don't use too much as it expands. It also "Runs" because it sets very slowly. Place horizontally, front down after inserting the adhesive into the front and both sides. Inspect it regularly as it sets. Moisture sets it off. It's dry where I am. Took hours. I understand there is a faster setting version. For the original adhesive, putting the mag combo in the freezer for 20 minutes , then setting it outside for condensation to help set the adhesive may speed things up.

6 - Haven't fired with it yet, but ran a couple dummy rounds at the top of the mag from cocked bolt position and it fed them.

It looks great while inserted in the SMG. While utilizing the entire length of the Thompson 30 round mag, there may be room for 34 or 35 rounds of 9mm in this.

 

Attached Files


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#18 DUBLBZ

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Posted 30 July 2020 - 08:15 PM

Has anybody else tried this or something similar?

With several discussions on the subject of magazines for the UD42, I would have expected it.

For interest in just a "Shooter" magazine, there is now a new plastic drum magazine for the Colt style 9MM AR15. It looks long enough to incorporate into the conversion scenario described above. Should look a little strange, but would probably work well.


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#19 JimB

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Posted 08 August 2020 - 08:51 PM

The origin point for the kits sold Stateside years ago by Armex was allgedly Indonesia and were part of the pre war Dutch East Indies contract completion of which was interupted by the Japanese

Thats how they ended up being dropped to resistance units, there were a fair mess of them warehoused needing a home


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