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Old 11-19-2011, 05:49 PM   #1
I.Oak47
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Default ★★Left Side Folding stock?

Ok i dont know much about these guys, so help me, there is 2 differnt types of trunnions? 5mm or 4mm dont understand what is 4 or 5mm? theres the poly(full stock) and then the triangle deal, Can those be switched back & fourth on same trunnion...What country are these made? HAS any USA company made a copy of these trunnions?
★ And last: what trunnion is wanted more ?









Any one who drops knowledge; thank you much
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Old 11-19-2011, 06:43 PM   #2
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I.Oak47 - the lowdown.

Bulgarian 4.5 mm pin folders are based on old Soviet tooling. These are the most common demil kit folders and trunnions. Bulgarian side folding flats are based on these. They fold at 6 degrees. 4.5 mm pin Triangle and Poly folders are interchangable.

After the Soviet Union broke up the Russians improved their folders using a 4 degree folding trunnion with beefier 5.5 mm pin. These were for the AK-74M, dubbed AK-100 series folders. The 4 degree sweep locks up for a better recoil load path. If used in a Bulgarian flat the trunnion will stick out 2 mm at the very bottom of the receiver. I cut my own 4 degree receiver trunnion cutout from a fixed flat and it looks great. New Russian folders use both 5.5mm Poly and Triangles, interchangeable.
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Old 11-19-2011, 06:45 PM   #3
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Quote:
Originally Posted by I.Oak47
Ok i dont know much about these guys, so help me, there is 2 differnt types of trunnions? 5mm or 4mm dont understand what is 4 or 5mm? theres the poly(full stock) and then the triangle deal, Can those be switched back & fourth on same trunnion...What country are these made? HAS any USA company made a copy of these trunnions?
★ And last: what trunnion is wanted more ?
Get your notepad out, cause K-Var fu**ed it up along the way.

The Russians invented the bank-vault-solid side folder.

Originally, they used a 4.5mm pivot pin.

Current production uses 5.5mm pins.


Now here we go with reality:
Fact: Tens of thousands of AKS-74 kits (with triangle side folders) were imported a few years ago.
Fact: K-Var uses 4.5mm pivot pins in their side folders

You can install a K-Var solid poly side folder (current style) on a 4.5mm trunnion. This is because K-Var chose to have their poly side folders use 4.5mm hinges, so as to be compatible with all those AKS-74 kits.


As of now, the only place I know of to get a 5.5mm side folder is from overseas. Nobody in the USA sells them commercially.
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Old 11-19-2011, 07:11 PM   #4
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Above: Russian 5.5 mm 4 degree trunnion in a Bulgarian style 6 degree folding receiver.
It's fudging around with fit, lockup and pre-cut trunnion hole alignment.

Quote:
Originally Posted by nalioth
As of now, the only place I know of to get a 5.5mm side folder is from overseas. Nobody in the USA sells them commercially.
New Russian made Arsenal SGL 31-94 (poly folder) and SGL 31-84 (triangle folder) rifles imported by Arsenal Las Vegas/K-Var use the newer Russian 5.5 mm pin 4 degree trunnion because they are built on current AK-100 series tooling by Izhmash Izhevsk - so they are sold in the US as a component on these rifles.

Quote:
Originally Posted by I.Oak47
★ And last: what trunnion is wanted more ?
That is totally subjective to one's project and purpose.
4.5mm 6 degrees are the most common demilled kit component available.

If you're building on a Bulgarian side-folding receiver you need a 4.5mm 6 degree setup.

If you're a Russian AK-purist building a contemporary AK-100 series rifle then you use a 5.5mm 4 degree setup in a custom receiver or one of the current Legion receivers made for them.

They are also a vast improvement in lock-up stability and cheek weld to old Soviet under-folders, Poly more so than Triangles for either 4.5 or 5.5 mm pin types.

.

Last edited by He219; 11-19-2011 at 07:27 PM.
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Old 11-22-2011, 09:13 PM   #5
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I built one with a mix of the parts - unknown to me until I started to document all of the parts and later try to put the thing together. I had a triangle folder (diameter 4,5mm pin) from Ukraine, and a complete "solid" polymer folding buttstock kit (diameter 5,5mm pin) from a U.S. supplier. I also acquired two (02) NDS receivers for this model of AK-74.

I measured the hole pattern of both the rear trunnion and the receiver and thought I made some mistakes when I did a stack-up with a CAD programme. So, I made the measurements again. At that end I discovered the 1.5 degree difference in the design of the parts. I knew that was too much variation to be caused by manufacturing errors.

So - I shifted some hole locations a bit and got just what I wanted on the first rifle. I also set up the triangle folder and carefully resized its pivot hole to diameter 5,5mm. I do like the ability to interchange parts.

At the moment one (01) rifle is still waiting for the rear trunnion to again become available. If it does not become available soon I will machine one from the solid since I have a part drawing of it and all of the other parts.

I don't expect to ever sell such things as the cost to manufacture a few is prohibitive when done on manual machinery and then the parts must be heat-treated. The cost for a few special cutters alone is going to be about $100.00 since I can't find any good ones on the used cutter market.

So, I am holding off the manufacture for the time being and hoping that K-VAR soon has the rear trunnions again - I am on their contact list when it becomes available. I have enough small parts so the only thing required to make is the cylinder & hook latch and that one is not so cost-prohibitive to make.

Best Regards,
Robert Forbus
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Old 11-22-2011, 11:25 PM   #6
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What would sell out faster ten 5mm trunnions of 10 4mm trunnions?
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Old 11-28-2011, 05:20 PM   #7
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I.oak47,do you have a source for triangle stocks? I want to build a "Khyber pass" AK .
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Old 11-28-2011, 05:27 PM   #8
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not yet, hope to have somthing in future worked out. I see them on here but costly.
Quote:
Originally Posted by gunnerdog
I.oak47,do you have a source for triangle stocks? I want to build a "Khyber pass" AK .
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