Friday, April 13, 2012

Suomi M31, M-31, Kp31 parts kit building.

This is a post intended for everyone of my readers who have been lead here by a search engine while you look for information on building a semi-auto Suomi out of a parts kit.





If you want drawings, I still have them, and offer them to anyone who wants them.
Best of luck to everyone who has acquired one  of these kits while they are still cheap.


24 comments:

  1. Replies
    1. Anonymous,

      Please email me. It varies slightly.
      theredneckengineerATgmailDOTcom

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  2. Hello, I have been reading my way through your blogs and I am very impressed with your work here! I am thinking of a Suomi as my first heavy duty smithing project and your posts are invaluable. One question I had concerned the barrel mods that need to be made. When stretched to 16+ inches dose the new legnth of barrel need to be rifled? I guess Im wondering if it would be good enough to permanently attach a compensator or even a legnth of pipe/tube to the barrel with a larger i/d than the barrel as a simple solution?

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    1. Andrew,

      First off, thanks for reading and thanks for your kind words.
      Second, I forget where I read it, but I read that in the case of smaller, non magnum pistol calibers such as the 9mm, having a rifled barrel longer than 8" was pointless. It just doesn't assist the accuracy much at all past that point.
      Every barrel I stretch on these kits simply has a piece of 4140 round stock drilled out to 3/8" all the way through, and ..50 on one end so it can be pressed on the end of the original barrel after I turn down a one inch long section to .505". The two sections are pressed together between centers on my hydraulic press and then welded together.
      You can port the extension as much as you see fit, but its really pointless. The gun is so heavy that recoil is nonexistent. It's like shooting a .22 with some balls behind it.
      These little carbines are 100 yard steel gong killers. Every one I've built for my own collection has been boringly accurate, you stick the front sight on what you want to hit and then just dump a drum into it. The muzzle doesn't hardly move due to the weight of the gun, so as long as you have good trigger control and don't jerk it, you will have no problems keeping an entire drum on target.

      Hope this helps, good luck with your build!!

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  3. Thank you for the info! I suspected as much and I will still seek local legal advice anyway before I put anything together. Another idea struck me today looking at AK pistol builds (an AK kit is also in my future) what do you think of a Suomi pistol? Being a piece of scrap in legal terms should mean you can build the reciever as a pistol so long as a stock can not readily be attached. The barrel wouldnt need to be touched and you wouldnt be limmited to the 10 parts rule, though you would still need to make it semi without the ability to accept FA parts.

    Just a thought exercise right now lol, I havent handled one yet but it sounds like even destocked it would be a pig and not fun to hold up one handed.

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    1. There are lots of homebuilt Suomi pistols out there, for the exact reasons listed.
      I can say firsthand that yes, they are very unwieldy and heavy, but there's something about being able to carry an old SMG under your jacket as your CCW piece that's just SO attractive to me.=)
      Once the receiver is torched, it is scrap metal in the ATF's eyes, so whatever you build it to is up to you.

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  4. Lol, I had visions of a CCW Suomi with drum mag! I googled Suomi pistol and came up with nothing, but then there dosnt seem to be much blogging going on about these things. Cool by me, keeps the price under $100 and I bet all my gun buddies will think its a Thompson. Hopefully the prices dont get stupid with the election.

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    1. I think if you want one, get one. The election has already been affecting prices on them, given how many people email me every week asking about how to build them.

      If you want to see some cool Suomi stuff, join the Guild.
      www.weaponsguild.com
      if it asks how you found out about the Guild, tell 'em I sent you.
      All kinds of awesome homebuilt stuff on there, and it's a great group of freedom loving individuals who all love building guns.

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  5. Thank you, I will checkout the guild for sure. Im caught between buying something in the grab thats going on now or waiting for the clamoring to die down. But with these being a fixed comodity and so many people discovering them I dont see the prices going down at all.

    I noticed you are not providing the 80% services any more, That sucks for genuine enthusiasts who lack the resources to complete a build alone. 6 weeks is far from an unrealistic period as most hobby level builders couldnt pull off one rebuild in that time let alone several along side other projects. I'll be gathering every bit of info on these builds I can so please do post up your drawings.

    Also I was thinking that as the recievers you show seem to be largely new material do you think a totaly scratch built reciever might be more straight forward than salvaging original components onto a scratch built cylinder? On the other end of the scale how plausable would it be to build a jig and rebuild the reciever through building up new material using a wire fed/stick machine? I think its doable with an AK using a formed copper negative backer to reduce cleanup and final fitting.

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    1. My suggestion is to buy kits at their current prices, they aren't making any more of them, and they make for fun projects. Some people have used the parts to make Thompson replicas in 9mm, 45, and .40, you're not just limited to building a Suomi out of them.
      The pre-built Suomis are nice if you just don't have the tools necessary to build one, but on that note, plenty of people have built their kits using parts from HellboxArmory and a few others, with nothing more than a drill and dremel. It just gets expensive that way. When I was doing the 80% stuff, you could buy a kit for under 100 bucks, then pay me 200-250 bucks to do all the hard machine work, then the rest was just a matter of you taking your own time and tools to complete the parts into a working firearm.

      I won't divulge the issues behind the 80% case beyond what I have written on this post, I don't see any point in naming names. I am now devoting my time to building my own parts kits and helping friends build theirs; i.e. I allow good friends of mine to come use my machine tools in my garage.

      Definitely join the Guild, and see how plenty of people build the Suomi without a machine shop. One of the easiest ways to do it is to buy a reweld kit, it fits over the torched original receiver and allows you to weld it back together into one piece, while also keeping the original full auto bolt from working in the receiver unless heavily modified to the point it can no longer function as an open bolt SMG.
      Some guys have taken dimensions to their local machine shops and had them machine an aluminum welding jig for rewelding the original receivers. Others have just used a piece of copper tubing split down the middle to act as a welding backer jig, and filled in the missing areas with weld.

      My first Suomi was built on an entirely new machined receiver, check my archives for info. It was much more difficult than a reweld or the 80% pieces I sold/machined. Hence my desire to streamline the process.

      If you desire drawings, please email me. My email info can be found in the About Me on the sidebar.

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  6. Wow ashame people couldn't keep there mouths shut, another great help to the community lost, best of luck to you.

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    1. Anon,
      I still build kits for myself, and I still help my friends out in their builds. I also contribute to the Band of Brothers on the Weapons Guild, www.weaponsguild.com

      I am far from lost, I am still here building stuff.
      I just lack the ability to deal with the general public and random complaints. It seemed to me the easiest way to respond to the complaints was just to stop taking on new projects, plus while I was working on Suomi projects, I never had much to contribute to the blog with.

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  7. I've look at several Suomi kits at various sites. Do you have any particular site that you recommend. I noticed the site you suggested for the receiver a few post up, but would you recommend the rewrote kit or buy the 80% that needs a little drilling and drimmel work?

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    1. I think the 80% receiver is the way to go.

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  8. having a hard time joining weapons guild .com working on a kp 31 need help and cant email the redneckengineer for some reason

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    1. I haven't gotten any emails from anyone new.
      What problems are you having with the Guild?

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  9. can you email me at fredstrange1@hot mail .com cant get the answer right for group motto thank you for your time

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  10. builders helping builders is the motto.

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  11. are the plans still available? How much? logannicholss@hotmail.com

    Thanks

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    1. I don't offer plans, just blueprints.

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    2. I would like a set of blueprints if possible? I like the way you approached the build. your blog has been very helpful. I happen to have a Aircraft spruce specialty a few miles from me here in GA.
      The 4130 they have listed is 1,5 x ,188 wall I,D, 1.124 Did you ream or bore this out to 1.015?

      If you do have Blueprints or drawings can you contact me sdec@bellsouth.net

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    3. I did not bore the tubing out at all, and I sure didn't bore it to a smaller size. I don't even know how that's possible.

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  12. Do you have drawnings for the receiver for a KP-31 How do I contact you Thanks Eugene

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  13. Do you have a web link for a side plate template? Or do you have a PDF template you could email?
    Thanks!!

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