My STG-940 Project


The goal:




Current build status:  COMPLETE

 - Finished paint job and final fitting of stock parts.





Additional STG-940 images found on various websites:


Photoshopped conceptual rendering of STG with Galil buttstock:

Scan of an old write-up about the (now-defunct) US-built Stock Options STG furniture set.


PDF files of different industry write-ups from different sources.  About 2 MB each:







Of interest is that it is a "Wieger" which is a concactenation of the town and company name in which it was built.


 - Barrel sleeving and headspace complete.  Test fired OK.  Hand guard fabrication and painting are the only remaining items at this point:



The combination gas block/front sight was built in the same way as my AK-74 build... cut the front sight and silver braze to the gas block, then clean up.  The front sight is off of an E. German barrel stub.


I welded the gas port shut, ground it smooth, and then drilled a 90-degree gas port at the new location for the gas/sight block.



Barrel Sleeves

Trunion Journal Sleeve:

As you may already know, the Galil barrel is threaded and is a smaller diameter than an AK barrel.  I chucked the barrel in the lathe, trued it on the steady-rest, then cut the threads off so the trunion journal was smoothed.   


Afterward, I then ordered some 4130 seamless tubing from www.AircraftSpruce.com and reamed it to the proper diameter.  I pressed it on and viola! I have a sleeved barrel!  I chucked the barrel back into the lathe and lathed the journal down to fit the trunion with the proper clearance. 


Now to the muzzle.  The Galil muzzle threads are 13x1, and the AK threads are 14x1.  The goal was to use an AR-style flash hider like the factory STG build.  I repeated the same process I used for the trunion journal, except I used the threaded end of a discarded barrel section from www.AA-OK.com as the "sleeve".  The barrel section is sold for the front sight, and I never actually thought I'd use the cut-off barrel section - double bonus!  :) 

I *carefully* drilled the barrel from the back side, so that the muzzle end would not be out-of-round from the drilling, and got it large enough for my lathe bits to fit inside. 


I made this one a TIGHT fit.  It is undersized to about .006" tolerance, which is about what a Chinese barrel tolerance runs.  T-I-G-H-T!!!  The advantage here is of course that this will *never* "shoot off" even if it heats up.   


After the threaded sleeve was lathed out, I cut off the excess barrel section and cleaned up both ends.  I threaded the sleeve into the muzzle brake, and set everything in my 12-ton press.  Surprisingly, the fit was tight enough to flatten the penny that I used to protect the breech end.


Its on!  Side-by-side comparison to a Galil factory barrel.


I indexed the threads so that the flash hider ports don't vent directly into my line of sight - they vent to the 1 o'clock, 3, 5, 7, 9, and 11 o'clock positions when the flash hider is fully tightened.  This was another advantage to pressing it on WITH the flash hider in place!


Receiver Markings

I am basing the markings on the East German Trunion and Selector Markings.  The K3 in a circle seems to be the most common E. German DDR marking.  The AK Stampings Page indicates there is also a circle-in-diamond stamp that is from the same factory. 




Handguard tube is longer, and is built from 4130 steel tubing.



Buttstock retainer is based on the German push-pin (as with a G3) and provides a mount for the rear sling loop.  Buttstock is hollow with enough space to allow for a German .223 cleaning kit



Handguard Retainer 

The retainer was machined out of 1/2" stock that was drilled with holes large enough to slip over the barrel and gas block.  The retainer pin is based on the basic AKM retainer - a captive pin that rotates to engage the mating notch on the barrel.  The internal tab was welded in place to ensure it won't pull away.


The sling loop is held in place by the internal tab when the handguard is in place.  The internal tab is in the vertical position and is physically limited until the handguard is removed.