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Old 08-24-2014, 07:33 PM   #1
valleyrat
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Default Yugo three rivet rear trunnion (reference pics here)

I might be the only person who finds this interesting. Way back when the Yugo m95 kits were available ($425 plus shipping IIRC) I remember perusing the Zastava website and found pictures of a fixed stock version of the rifle (all of the kits available at the time were underfolders). The rifle in the pics featured a fixed stock with a three rivet rear trunnion, which, up until recently, was a part that was not available in the USA. This particular rifle also featured a grenade sight gas block, so you could think of it 556 M70 basically. Rifle pictured below, top rifle in pic:



Here are pics of this rear trunnion. The difference between this one and the one in the pic above is the receiver thickness. To use this on a 1.5mm receiver one would need to trim .25mm off each side and .5mm out of the slot next to the recoil spring recess (where the back of the upper rail fits into).







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Old 08-24-2014, 07:57 PM   #2
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Yes., I have noted the triangle rivet pattern Zastava rear block. Wonder why they bothered changing the pattern. The gas block is also similar but not a M70 pattern.
Dunno if the block was used with the receiver cover lock in the pictured rifle but the receiver was not drilled for the lock.
I have thinned M70AB1 rear trunnions for AB2 builds. Not a bad mod.
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Old 08-24-2014, 08:06 PM   #3
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Yes., I have noted the triangle rivet pattern Zastava rear block. Wonder why they bothered changing the pattern. The gas block is also similar but not a M70 pattern.
Dunno if the block was used with the receiver cover lock in the pictured rifle but the receiver was not drilled for the lock.
I have thinned M70AB1 rear trunnions for AB2 builds. Not a bad mod.
It is interesting to note there are other manufacturers who implemented the three rivet pattern trunnion in one form or another. Stamped receiver Valmet and also the Beryl immediately come to mind. They must have seen the need, like you I am curious what prompted the design change.


Another difference besides the gas block is the comb of the buttstock.
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Old 08-24-2014, 08:09 PM   #4
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Originally Posted by valleyrat View Post
It is interesting to note there are other manufacturers who implemented the three rivet pattern trunnion in one form or another. Stamped receiver Valmet and also the Beryl immediately come to mind. They must have seen the need, like you I am curious what prompted the design change.
All those rifles you mention are designed to fire grenades ( in their military specs, anyway ).

Perhaps the 3 rivet blocks are for enhanced durability with this in mind?
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Old 08-24-2014, 08:13 PM   #5
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All those rifles you mention are designed to fire grenades ( in their military specs, anyway ).

Perhaps the 3 rivet blocks are for enhanced durability with this in mind?
Id bet you are right. I have heard that recoil from launching live grenades is severe but I have not experienced this personally. I have read second hand that firing grenades from the under barrel mounted launcher on a maadi would actually bend the crutch folding stock.
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Old 08-24-2014, 08:16 PM   #6
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Here are couple of semi-auto 5.56 rifles imported by Mitchell Arms in the 1980's.



The M80 didn't go into production until 1985. Note the different hand guards and pistol grips on the folding stock model.
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Old 08-24-2014, 08:19 PM   #7
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^^thinner bbl profile on those compared to the m95. Interesting.
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Old 08-24-2014, 08:35 PM   #8
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A lot of countries beefed up their 5.56 AK's. The Valmet 71 to 76. The Yugo M80 to M90. Romania now has their 5.56 AK on an RPK type receiver. Russia uses better steel than earlier designs. Poland took several years to approve the final version of the Beryl. K-var now says the Bulgarian 5.56 recoil spring is the same as the others but the ones I have seem heavier. I wonder if something in the action timing might be harder on the 5.56 AK's. The gas port is close to the 5.45 size but the cartridge produces quite a bit more gas port pressure.
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Old 08-25-2014, 11:48 AM   #9
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A lot of countries beefed up their 5.56 AK's. The Valmet 71 to 76. The Yugo M80 to M90. Romania now has their 5.56 AK on an RPK type receiver. Russia uses better steel than earlier designs. Poland took several years to approve the final version of the Beryl. K-var now says the Bulgarian 5.56 recoil spring is the same as the others but the ones I have seem heavier. I wonder if something in the action timing might be harder on the 5.56 AK's. The gas port is close to the 5.45 size but the cartridge produces quite a bit more gas port pressure.
It would be fascinating to have access to the internal memos discussing these design changes. I suppose those are lost to history.
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Old 08-25-2014, 11:54 AM   #10
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It would be fascinating to have access to the internal memos discussing these design changes. I suppose those are lost to history.
Probably something like this>>>
"Hey Igor., SiberiaMart have big sale for triangle block for AK. Good news comrade., we will buy for AK" Drink Vodka!
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