Review *** Suomi M31

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12/7/2011

After several months of researching this wonderful old war horse, I decided to take the plunge and provide those interested an “Up – To – Date” review. I am referring to the TNW manufactured, semiautomatic, “reproduction” of the Suomi M31 submachine gun.
TNW Firearms, Inc. Manufacturers of the semi-auto 1919, M2HB and MG34.
This is the same gun that is available from several online sources, from $399.95 to $750.00. I purchased mine from “J&G Sales” for $399.95. This includes 1 36round stick magazine, and the option of purchasing 72round drum magazines at $19.95 each with gun purchase (extra 36round stick magazines are also available at $19.95 each).
Finnish M31 Suomi 9mm Submachine gun style, 16.25in.
I purchased mine with 2 72round drums and 3 extra 36 round stick magazines. For those straining at the bit to join me, here are a few websites you might want to visit. They have available a range of accessories that might strike your fancy, as they did mine (notice in the pictures I have a reproduction German MP40 magazine pouch, perfect fit for the 36round stick magazines);
Numrich Gun Parts Corporation
(lots of original parts and magazines, even the 50round “COFFIN” magazines. Use Keyword search “ suomi “)
Home (NICE original stocks and other KP31 “full auto” parts)
Military Antiques, Military Collectibles and Militaria IMA-USA.COM (interesting military items, this is where I got the MP40 mag. pouches)

So much for basic introductions, I have found opinions on this gun dating back as far as 2009. Some appear to be simple “early production – prototype” problems, others seem to be trial and error corrections. There have been many, real and supposed problems with this I have found throughout web forums. I will update this thread with further reviews of specific items pertaining to this weapon. I will report what I consider to be problems and resolutions as I come across them. I will also be doing a complete range report on different weight and types of ammunition I use with this weapon.
If you have any questions that I may be able to answer or investigate for you, please let me know.

FIRST IMPRESSIONS ARE - THIS IS MONEY WELL SPENT!
https://www.milsurps.com/images/impo...DSCF0705-1.jpg

https://www.milsurps.com/images/impo...DSCF0709-1.jpg

https://www.milsurps.com/images/impo...DSCF0711-1.jpg

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Very neat, my cousin is really interested in one. I'm just curious as to its accuracy, but it looks great!

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12/12/2011

After spending the last week, tearing down and putting together the new toy, here are some personal insights. This thing is a “BEAST”! Yes it IS HEAVY, but also a real solid piece of war art. I will get to the “He Aint Heavy, He’s My Brother” part of the review in a little while. First let me go back to the initial reception of the gun.
I ordered this weapon with extra magazines, (2) 72rnd drums and (3) 36rnd sticks. I expected to receive, like most milsurp rifles, a box of “COSMOLINE” with some gun parts in there somewhere. What I received was a bunch of cosmoline covered magazines, individually wrapped in newspaper, and a “BONE DRY” gun in a separate plastic bag. Having read older reviews of this gun, if people were getting theirs in similar condition, no wonder they had problems pulling back the charging handle. The first time I pulled mine back, such a loud screech came out of the receiver, I was sure something was broken. Just imagine that ancient rusted spring on the back porch door, now think of that sound coming from the delicate workings of your semi-automatic rifle. Yea, not on anything I’m going to shoot. Anyway, mental note have lots of your favorite lube ready when you get one of these.
I will get into some of the individual areas later, but FIRST this *** WARNING ***:
I had read earlier warnings about making sure the safety is NOT ON when pulling the charging handle. I am not sure if this could be done, but if you did I’m sure you would not like the results. The trigger group is set up so when the safety is “ON”, the trigger is disconnected from the striker, and the striker is locked. If the striker is in the “FIRED” position and the safety is “ON”, the striker will be locked in the way of the bolt as you pull the charging handle. Always make sure the gun is pointed in a safe direction, and the safety is “OFF” in the fire position, before pulling back the charging handle. With the safety off, if the striker is in the “Fired” or “Cocked” position, you can pull back on the charging handle. If the striker was in the fired position, it will just rotate back and lock in the cocked position. If it was already cocked, the bolt will just ride back over it as the charging handle is pulled.

NOW to the biggest question on everyone’s mind:
HOW HEAVY IS IT?
Almost every posting about this weapon has the obligatory comment; “That is really HEAVY. . . “
After the past few days taking apart and putting it back together, I seem to forget about the weight issue. This is just such a solid piece of machinery; the weight is a natural part of it. I would almost think something was wrong if it didn’t weigh as much as it does. To simply state that this thing weighs in at a hefty 12.5lbs is hard to imagine. I thought I would give a little show and tell;

M1 carbine with (3) empty 15rnd magazines
https://www.milsurps.com/images/impo...12/CARBc-1.jpg

Yugoslavian M48b
https://www.milsurps.com/images/impo.../12/M48c-1.jpg

Yugoslavian M59/66a1 with 3-9x32 scope
https://www.milsurps.com/images/impo.../12/SKSc-1.jpg

Here she is – Suomi M31 with empty 72rnd drum magazine
https://www.milsurps.com/images/impo...2/SUOMIc-1.jpg

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Nice post and information.

I picked one of these up at J&G's booth at a recent gun show and my first thought was, "I'd sure hate to have to carry this very far or for very long." The weight seems to be condensed kind of like an ingot.

It was well made and a nice clean finish on the display model. Since I had just arrived I thought I'd come back later but I got the gun show worn out shoes and never did go back.
I liked the looks and will see what you tell us re: operation, reliability and accuracy.


AZB

UPDATED 12/13/2011

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12/13/2011
Let me see now!
Having hit some of the main spots so far; it looks like a good time to step back and take a look at what we have here. From seeing some of the chopped up “Original” parts kits, I would say this gun started out as a classic blued steel and wood war horse. What I have is a very nice utilitarian parkerized version of the same. I have read reports that a little wiping down with “0000 steel wool” and “KROIL” will smooth the parkerizing to a more subdued finish. I think I will try this on the bolt first, as I hate the idea of this rough metal ramrod slamming back and forth in front of my face.

Bolt bottom looking into slot for striker to hit firing pin.
https://www.milsurps.com/images/impo...DSCF0723-1.jpg

If that works out the barrel and shroud would be next on the list. My understanding of earlier versions of the barrel is; TNW used the original 12.6” barrels with an extension tube welded on the end to obtain the legal 16” length. My newer version has a FULL length 16” rifled barrel. This may actually lead to improved accuracy (not that you could tell by my shooting abilities).

Notice the sharp lands and groves at the muzzle of this full length barrel.
https://www.milsurps.com/images/impo...DSCF0717-1.jpg

The original Suomi M31 had several different barrel shroud configurations. The first type ended just forward of the front sight, and was cut at a shallow angle. The barrel ended at this point and just barely could be seen protruding from the end. The next type was the addition of the muzzle compensator at the end. This was just a sleeve welded to the end of the shroud, with holes drilled in the top, and a restricting “nipple” at the end. The shroud I received has the compensator, but has been bored out so the legal length barrel can protrude through. This actually only extends the overall length by a couple inches. Remember the original barrel would have gone only as far as the front sight, the rest of the shroud and compensator would still be out there.

Barrel shroud with compensator (non-functional with a legal length barrel).
https://www.milsurps.com/images/impo...DSCF0713-1.jpg

For those that are interested in “SBR”. This is very easy to do, though why would you. From the looks point of view, you will only lose at the most 2” of length. You may lose accuracy. You WILL lose money (I’m from the government; I’m here to help you!). Anyway if you must, pay your dues, get your stamp, and purchase an original barrel and shroud. Then just put them on instead of what you have, and wish you could actually run this baby at 900 rounds per minute.
Original parts can be found here;
Home (NICE original stocks and other KP31 “full auto” parts)

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Well, I got my Suomi M31 today. A real piece of history. Can you imagine holding off the Russian military, twice! As I opened up the packaging, I saw a small piece of paper indicating that it was test fired by someone with the initials J.E. I started to take the gun apart to clean it and get familiar with it. No manual was included so, I went to the TNW (manufacturer) sight and made a copy. I proceeded to take it apart and the parts shown in the manual didn't match the parts that were in the gun. I called TNW and spoke with a pleasant guy by the name of John. He answered all of my questions and then I told him that the gun was completely dry. He said its best to keep it that way or they have a tendency to gum-up. I told him that I could barely pull back the bolt lever and I asked about the coating on the bolt itself. He said that I could smooth it down some if I thought that it was a problem. Bottom line is that I will lube it lightly and see what happens. I am anxious to get out to the property, to give her a try in a few days. Bill

Bill,
Congratulations on your new toy! I’m sure you are going to have a lot of FUN! I have been slack in my updating of this thread so I hope this latest info helps.
My M31 was also VERY DRY when I received it. I tried a quick trip to the range as is and was lucky to get more than 3 or 4 rounds through in succession, before a misfeed would occur. After three attempts I called it a day, and returned home for “Clean & Lube” time. I used a small amount of “Molly Lube” rubbed all over the bolt, a liberal spray of “Remoil” to the feed ramp and magazine port area, and a half hour soak of the trigger assembly in a container of “Kroil”.
I loaded up; my 2 drums, each with 70 rounds of bulk 147gr FMJ ammo, my four 36 round sticks held a mix of 117gr, 124gr, 147gr, FMJ and HP. Back to the range I went. My purpose was more functional test rather than accuracy. One of the stick mags had a problem with consistent feeding, about every 3rd or 4th round would not feed correctly. I later noticed what looks like a dent in one of the feed lips on this mag? One of my drums seemed to have no problems, as long as I fired slowly. If I tried to rapid fire the 3rd or 4th round would misfeed. The other drum had this misfeed problem in slow and fast fire testing. I have since done the adjustment procedure to the first drum, and am HAPPY to say I can EMPTY a 70 round drum in NO TIME!
Here are some pics of the DEAD PAPER!

SLOW DRUM 10yards:
https://www.milsurps.com/images/impo...12/DrumS-1.jpg

FAST DRUM 10yards:
https://www.milsurps.com/images/impo...12/DrumF-1.jpg

I am currently building one from a kit and I'm very anxious to be able to shoot it

mdrim13

I do have one of these beasts and see why it was so easy to control in autofire. Interesting to note that the gun uses the air behind the bolt as a pneumatic buffer to control the rate of fire. In the receiver cap is a small adjustable vent for that purpose. Mine came with a ton of white grease on the bolt and spring and functions fine. I did not clean it off as I saw no dirt or machine leavings to worry about. The stock was dry and rough, but I left it rough to show the lathe marks and coated it with a couple of layers of the ever popular shellac. I have the welded on barrel extension, which does not seem to affect accuracy. I would like a bolt hold back for use on the range and for cleaning, but removing the barrel is easy enough so why worry. I did remove the stock and clean the trigger group, and would like to give it a bit of tune up to make the trigger have better feel. Just for your information, Allegheny Arsenal has PPSH 43 mag pouches that work with the drums and stick mags. They will most likely send you unmatched pouches if you order more the one, which I cannot understand. The order fold just do not seen to care about pleasing the customer, the owner is a bit better but not much.

12.5 lbs, empty.If you run out of ammo you can use it as a club and beat them to death.

New guy here
Thank you for the fantastic post . I just recieved my m31 last friday . This is definetly a work of art . Can anyone tell me what type of ammo is best to run through this beast . And just an observation . i noticed that in the service manuals available on the net that they all have the end cap and bolt coming out before removal of the barrell . call me paranoid , but can i remove just the barrell and shroud without removing anything else first on the semi . again - great post , any info would be greatly appreciated ..