Modification Of The Rear Or Front Trunnion Block Of Your M85 Or M92 Rifle


Finally! Do You Need The Rear Block Of Your M85 Or M92 Krinkov Kit Modified For The Folding Stock? I now offer the service of machining your virgin M85 or M92 rear block (or rear trunnion as some say) that came with your kit so it can accept the Yugoslavian underfolding stock hardware. What do I do with your virgin block? I ream the rivet holes to their correct diameter 4,6mm and 4,1mm size, and then machine the pivot hole, the locking lug holes, and finally make the clearance cuts for the pivot pins.


I will also make your M85 breech block ready to use if you want this done. If you ship it with your rear block I will do it for the low price of $10.00. What do I do? I drill the missing diameter 4,1mm rivet holes; ream the lower rear rivet holes to diameter 4,1mm; ream the lower front rivet hole to 4,6mm, and drill a diameter 0.250" pilot hole for the diameter 7,0mm barrel pin. Please note that when I drill the pilot hole for your barrel journal - I will not drill it all the way through. That is best done after the barrel is pressed in and headspace made correct.


The pilot hole size allows you to use a diameter 0.250" dowel pin for alignment in your drill press. Please note that the breech block is quite hard, and I recommend using a drill bit of excellent quality such as a McMaster-Carr P/N 2908A44 . This is a short, stiff drill bit that we refer to as a "screw machine drill bit". For best results do not exceed 400 RPM when using this drill bit and use a good quality cutting oil! You can follow this first drill pass with a larger drill, and finally a diameter 7,0mm reamer. It is important to use a short, stiff drill bit since you do not want the drill to wander towards the softer metal of the barrel.


NOTICE! The Zastava (Yugoslavian) underfolding stocks are very hard to find now - especially the 4/8-rivet version for the stamped receiver rifle. A Polish or Hungarian underfolding stock will look very much like the 3/6 rivet version used on the milled receiver Zastava (Yugoslavian) rifle and can be used. But - it requires a different locking hole pattern and if this is what you plan to use I must know before I cut the hole pattern. Once the locking hole pattern is cut for the Polish or Hungarian underfolding stock the Zastava (Yugoslavian) stock will not work correctly.




How much? Send me your virgin block and I will return it as a finished unit for $30.00. Yes - that price includes return shipping by USPS Priority with a tracking number. For $10.00 more I will correct the holes in your virgin breech block (or front trunnion as some call it) so both blocks together will cost $40.00 - and again that includes return shipping. If you want $250.00 of insurance - just add $5.10. I'll work it out below:


One (01) M85 or M92 rear block machining = $25.05

One (01) USPS Priority with tracking = $5.95

Total = $31.00 - if you want $200.00 insurance it will be a total of $36.50


One (01) M85 or M92 rear block machining = $25.05

One (01) M85 or M92 breech block machining = $10.00

One (01) USPS Priority with tracking = $5.95

Total = $41.00 - if you want $200.00 insurance it will be a total of $46.50


If you have multiple (at least three of the same type) blocks we can discuss a 10% discount for the machining. As long as all of the blocks will fit inside a USPS Priority Small box the shipping cost will be the same. You might want more insurance - I'll have to get a price for you.


Please note that I will remove any burrs from the edges and make sure the sides are parallel before I place the virgin block in the milling machine. This, combined with the deburring afterwards will remove a bit of black oxide from the surface.


I know that I don't even have to mention this fact to most enthusiasts; but I feel I must remind everyone who wishes to modify their "Krinkov" that: Your M85 or M92 has a barrel that is less than 16" from muzzle to closed breech. As long as it is built as a pistol (check your State laws!) and does not have any kind of fixed or folding stock it should be fine. Federal BATFE regulations state clearly that a rifle must have a barrel that is at least 16" from muzzle to closed breech, and at least 26" overall with the folding stock extended.


In order to make this modification legal (make sure your State allows it!) you must extend the barrel length by permanently fastening a barrel extension (such as a fake booster, flash hider, etc.) of sufficient length to the muzzle so that the measurement from the closed breech to the new end of the muzzle is at least 16". This must be done before this block is riveted into your receiver! Failure to lengthen the barrel will result in possession of a SBR (short-barreled rifle) that is legal only after a tax stamp is obtained.


I will not go into further detail than this - read the BATFE regulations as well as the laws of your State.


Mail-To Address:


Ing. Robert Forbus

4415 Betts Road

Greenbrier, Tennessee 37073 USA

615/667.1304 facsimile

615/390.5645 handy e-mail website



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