Building a KP-44 semi auto SMG pistol

by Jim Green, Gunsmith on January 10, 2012

The KP-44 submachinegun was fielded by Finland during the Winter War against the Soviets in 1939. The Russians had such respect for this fearsome close in weapon, that they copied it themselves, and developed the PPS -43 in 7.62 X 25. My latest project is to build a KP – 44 pistol chambered in 9mm Luger.

After all my parts came in from Centerfire Systems, I went online to the Weapons Guild Forum. This website has a LOT of information on converting machinegun parts into into legal to own semi automatic carbines and pistols. As I don’t want to make a barrel extension to lengthen it to the required 16 “, I will simply weld the folding stock in place, to make this a ” pistol. “

 

 

I decided to start in no particular order. So I pressed the home made trunnion onto the barrel first.

 

 

The 30 ton hydraulic shop press is handy to have for work like this.

 

 

The next part of my process was to lay out the barrel and trunnion, then fit the feed ramp and shelf bracket into the stamped sheet metal receiver.

 

 

The feed ramp and trunnion support bracket are TIG welded together.

 

 

Then TIG welded onto the recevier.

 

 

I don’t want the sheet metal to get too hot and warp. So while the welds are cooling a bit, I decided to strip all the full auto parts out of the lower receiver, and toss them into the garbage can. I don’t want ANY full auto parts anywhere even in the same room with this build going on. No excuses to have the Feds come in and accuse me of building an illegal automatic weapon. Of course there’s a couple of parts that I will need to keep from the receiver, but NONE that will allow full auto firing. More on this later….

 

 

I measured the length I’d need on the sheet metal recevier repair section. This is soft 14 gauge steel. I cut it off with a hacksaw……

 

 

Then TIG welded the rear section from the original receiver. Since this will be a pistol eventually, then I will TIG weld the stock into a folded position over the receiver. More on this later…..

 

 

In this picture below, you can see the parts laid out together to give you a rough idea of what the KP – 44 semi auto pistol will look like when finally assembled. None of the final assembly is even ready yet. We still have a long way to go.

 

 

This KP-44 semi auto pistol will feed from the original 36 round stick magazines, or from the 71 round drum in 9mm Luger caliber. By law, you can only have a maximum of 10 foreign made parts in your gun. Section 922(r) will give you the list. This gun will have a total of only 8 by the time the gun is finished. Therefore it will be legal to own in the US.

Tomorrow I will start working on the bolt assembly. The original KP-44 fires on full auto only from an open bolt using advanced primer ignition. This pistol build will fire from a closed bolt in semi auto only. The bolt will be drilled out, I will make a firing pin, and modify an AK – 47 trigger and hammer pack available from TAPCO ( the G2 trigger ). This will satisfy MOST of the ATF requirements for this project. I will also STOP working on the receiver at this point. Beyond what’s been done here today, I am required to engrave a serial number and the company logo on the gun. I will wait until I have the TAPCO parts installed and the bolt properly modified before I continue with the receiver. It’ll still need the rear sights welded on, the ejector port cut out, and the rails for the bolt welded in. ALSO, a denial pin will be installed in the upper part of the receiver. This denial pin will prevent any future attempt to install a full auto unmodified bolt into this gun. More on all this later….

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{ 2 comments… read them below or add one }

Thomas P. Anderson February 14, 2012 at 5:05 PM

Hello, I just came across your website while googling the KP-44 pistol. I was wondering if you build these pistols for resale? I live in Minnesota and my neighbor has a FFL, so I would like to know if you would be willing to sell and price for custom build pistol? Thank you!

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Thomas P. Anderson February 21, 2012 at 3:32 PM

Hello again, I was wondering if I got hold of a KP-44 parts kit, what other parts would I have to get to build a pistol, carbine and/or a SBR? I don’t know if you have an NFA/Class II mfg. license but maybe that has to be done in Minnesota with NFA paper work? What TAPCO parts are required for the build? I think Military Gun Supply has the receiver repair section? Wild Horse Mfg. barrels, trunnion, feed ramp ( better than the factory)? Firing pin set up? What do you suggest? Thanks again!

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