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Discussion Starter #1
So what does a Russian AKMS trunnion look like? I haven't been able to find any info on this except a photo of an early Russian AKMS trunnion. My understanding is that only Izhmash made a AKMS and that the rear trunnion is the cast type, not the sheet metal type common to the Polish and Hungarian AKMS. I picked up a AKMS trunnion on a whim, it was sold as Bulgarian, but I am not sure if Bulgaria ever made a domestic AKM - or if they just assembled Russian parts.

The part I got is virgin and has no markings. It 'rings' when tapped, so I am assuming it is made out of a hardenable steel.



 

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I'm pretty sure this one can't be Russian, unless it's a replacement part made at Tula I(Tula did make some small number of AKMS rifles back in the mid-1960's). In any case, Izhmash kept the sloped lugs of the 1960-61 style AKM fixed stock trunnions on all their AKMS rear trunnions throughout the production lifespan of the AKMS and AFAIK they all have that style (on both the early three, and later, five rivet versions).

The one in your image has the stepped lugs as you'd see in a mid-60's and up fixed stock izhmash or Tula AKM. It would also be odd to have a Russian major part of this type without any pre-finish manufacturing check proof mark. Especially if it came from Tula. As you surmised, only the Poles made those sheet metal composite-piece trunnions, but they also made standard Russian types (machined trunnions) back in the old days. They generally proofed stuff, too. I can't remember what type the Hungarians made, i.e,. sloped or stepped, but I am pretty sure it's the sloped version since they are a pretty old school stuck-in-the-60's type rifles. I sold all my Hungo underfolders so I can no longer check. What do the Romanians use? It looks kinda Romanian to me. At the present time, i can't think of who else might use these stepped (recoil guide lugs) folding stock trunnions. Too many meds tonight, hehe. Somebody with experience with handling Romanian underfolders needs to chime in.

I do agree with what you originally stated, in that I highly doubt the Bulgarians made this part.
 

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FWIW – The rivet spacing is not the Romanian pattern, so I doubt they made your part. Even the Dracos with solid UF rear trunnions retained their unique Romanian UF rivet spacing.



The Hungarian UFs I have examined all used a cast rear trunnion with some final machine work, though earlier rifles may have had milled rear trunnions. Good photos of a cast one here.
viewtopic.php?f=17&t=141117&p=1133439&hilit=Hungarian#p1133439


I have a milled Polish UF rear trunnion (AKM pattern – not milled rifle) and the machining looks similar – especially the two holes on the underside. I can’t help but wonder if your part is a virgin Polish part. I know some virgin Polish front trunnions were imported some time ago, makes sense that some rear trunnions might have come in as well.

Is the width of your trunnion the correct width for a 1mm receiver?

Tantal said:
As you surmised, only the Poles made those sheet metal composite-piece trunnions.
I always thought the Poles were just following the Russians in that aspect. So all Russian AKMS rifles have a "solid" rear trunnion – even up to 1977?

Did they go from a milled one to a cast one in later production?

I admit I haven't studied the Russian AKMS rifles to the level I have the AKMs.
 

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MPiKM-72 said:
So all Russian AKMS rifles have a "solid" rear trunnion – even up to 1977?
Did they go from a milled one to a cast one in later production?
Yeah, Russian UF trunnions were all solid one piece parts, all the way up to 1977. The only major change they made I am aware of was going from a three rivet to a five rivet design in the mid-60's. The late ones might be a casting instead of a fully machined part, but they are heavily machined to the finished form, and look about the same in all design aspects. I'll have to get some out to give you a batter indication of whether they start out as a casting or not, but they have always looked heavily milled to me.

After checking online, the only trunnions i have found so far that actually used these stepped recoil lugs at the top were Yugo's and US made versions, but I'm sure others might have, too. You could be right and this might be Polish, although most of the milled Polish (not the stamped sheet metal weld-ups) that are identified as such have the angled lugs and are not stepped. There is, however, an Apex-sourced image of a take-off fully finished UF trunnion with steps that they sold, or still sell. But they don't appear to say where those came from. Must be Polish? If so, then they must have made at least three different versions of UF trunnions.

Thanks for your additional information, and the link to that great Hungo write-up you did. that was one swell kit! I did not realize all Romy underfolders, even the early ones, had that different Draco-type rivet pattern, compared to Russian. Learn something every day!
 

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Discussion Starter #5
Thank you both for looking at this for me. It sounds like it is not Russian or Hungarian.

MPiKM-72 said:
Is the width of your trunnion the correct width for a 1mm receiver?
Yes sir, it fits perfectly inside a AKM receiver. I would love to see a picture of the cast Polish rear trunnion with similar features.
 

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I'm relatively new to AK series rifles and my experience with them is limited to the few rifles and parts kits I own, but looking at my Romanian AK's (WASR-10/63, Draco, and G kit - all using military parts), my Polish (underfolder kit and "Hellpup" made with military parts), and my Soviet/Russian (2 '69 Izhevsk kits, '72 Izhevsk kit, and Saiga) and what ever photos on the web I recall looking at, it seems that that notch on the top of the recoil spring retaining block, above the backing plate, like this trunnion has, is something I've seen only on Polish rear trunnions.

My Polish UF trunnion is 5 rivet version that has a milled rear recoil spring retaining block with the side and back plates welded to it, and my Hellpup has a 2 rivet donut-hole milled rear trunnion with the backing plate welded to it. Admitedly the Hellpup trunnion is not an underfolder, but it does have that notch in the top of the back of the trunnion, above the backing plate.
 

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Marcus said:
....it seems that that notch on the top of the recoil spring retaining block, above the backing plate, like this trunnion has, is something I've seen only on Polish rear trunnions.
Keep in mind that all Russian AKM rifles made since 1963 have had those same exact type of steps on the recoil lugs of the rear trunnions, but it's just a feature of the fixed stock rifles. They never transferred that sort of lightened design to the underfolders AFAIK. Due to that early changeover date (from slopes to steps), a lot of Warsaw Pact countries started out using those stepped lug rear trunnions from the very beginning of their production lifespan, depending on when exactly they went to building stamped receiver rifles.

One thing to note is if the entrance to the recoil guide notch has side tapers on it, as early milled fixed stock trunnions don't have any to speak of but almost all of the investment cast parts from later years will have very obvious funnel tapers to help guide the recoil spring guide into it's channel. Not having them sorta says old school/milled version, or a copy of that pattern.

But anyway, I'm leaning towards this possibly being Polish. Did the seller actually state it was from Bulgaria? They certainly bought a ton of parts from other countries for their AKM rifles. Mostly Hungarian and Russian.
 

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Discussion Starter #10
Tantal said:
Did the seller actually state it was from Bulgaria? They certainly bought a ton of parts from other countries for their AKM rifles. Mostly Hungarian and Russian.
Yes, it even shipped in a bag that called it: Rear trunnion, Bulgarian, Excellent to like new, Underfolding Stock.
 

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Tantal said:
Marcus said:
....it seems that that notch on the top of the recoil spring retaining block, above the backing plate, like this trunnion has, is something I've seen only on Polish rear trunnions.
Keep in mind that all Russian AKM rifles made since 1963 have had those same exact type of steps on the recoil lugs of the rear trunnions, but it's just a feature of the fixed stock rifles. They never transferred that sort of lightened design to the underfolders AFAIK. Due to that early changeover date (from slopes to steps), a lot of Warsaw Pact countries started out using those stepped lug rear trunnions from the very beginning of their production lifespan, depending on when exactly they went to building stamped receiver rifles.

One thing to note is if the entrance to the recoil guide notch has side tapers on it, as early milled fixed stock trunnions don't have any to speak of but almost all of the investment cast parts from later years will have very obvious funnel tapers to help guide the recoil spring guide into it's channel. Not having them sorta says old school/milled version, or a copy of that pattern.

But anyway, I'm leaning towards this possibly being Polish. Did the seller actually state it was from Bulgaria? They certainly bought a ton of parts from other countries for their AKM rifles. Mostly Hungarian and Russian.
It's actually not so much the notch in the middle, but the way the metal goes up higher on each side of it. None of my 4 Soviet rear trunnions - 3 earlier milled "donut" and 1 later cast "forked", or my Saiga rear trunnion, have this, only my 2 Polish ones.
 

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I believe I have the same trunnion marked as Bulgarian. I am now starting to think if it is new chinese knock offs. If you look at it carefully it appears to be cast judging by sharp mold lines and i believe it has spue connections on front inside top and bottom just behind front rivet hole:(
 

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Not an M92 rear trunnion as those lack the vertical rear ledge on the trunnion.

It looks like one f the two types of odd ball trunnions that Tennessee Gun Intl sells. One has the rear tang and the there is semi virgin like the one pictured. Believed to be Bulgarian.

AK-47 Rear Trunnion Pistol Type [P1] - $55.00 : TGI Online Store, Your Source For Military Surplus Parts and Accessories

AK Underfolding or Pistol Trunnion [BA-BB-003] - $30.39 : TGI Online Store, Your Source For Military Surplus Parts and Accessories
 

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I beleive they are all from the same batch, pretty sure mine is exactly the same as top one for 55.00. I don't think they are Bulgarian unless its just some civvy company in Bulgaria that is making them . You can plainly see where mine was cut off from sprues so I'm sure its cast. Sometimes you have to get it in hand to know for sure, so 45.00 lesson for me.
 

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These are probably knock off airsoft parts from Taiwan. They share the same step profile exactly of the Asian sidefolder rears, as well as they do not meet any of the comparisons to real AKMS parts from any country, they are the closest to Hungarian cast AMMS rears though not the same. There is a small possability that they are ISD Bulgaria products but not likely, though one of the two (either Bulgarian non-military production or Asian imports) Both use good steel usually that is either treated or heat treatable.
 

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These are probably knock off airsoft parts from Taiwan. They share the same step profile exactly of the Asian sidefolder rears, as well as they do not meet any of the comparisons to real AKMS parts from any country, they are the closest to Hungarian cast AMMS rears though not the same. There is a small possability that they are ISD Bulgaria products but not likely, though one of the two (either Bulgarian non-military production or Asian imports) Both use good steel usually that is either treated or heat treatable.
They are milspec high quality. Used on some early import builds and some funky thumbholes. I have handled them before. They pre-date any Air Soft items as well.
 

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The simple fact still remains that they do not match any countries factory military spec. AK part. Its an aftermarket part, while built with a decent tool steel none the less, but still unclear as to the origin.
 
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