First off I want to say that I love my PSA AKs, I currently have 4 and have had a total of 6.

The folding mechanism is ridiculously tight. I had bought the JMAC 4.5mm hinged, M4 stock adaptor to replace the SB triangle pistol brace. I could not even push the release button to open the hinge, I had to lightly tap with a hammer, then there was no way the JMAC adaptor would even fit, measuring on my digital calipers showed the JMAC adaptor a fair amount bigger than the opening on the hinge, then when I measured the original folding hinge adaptor (with pic rail) it was really the same size as the JMAC. So basically someone at PSA had hammered the adaptor in and you can tell by the marks on the PSA adaptor! WTF? Now, I have filed down the original PSA part to fit and it still does not want to close all the way, it looks closed but the release button will not close.

So, do I need to file down the rear trunion or keep working at the PSA and JMAC part?

This is my first PSA AK with a folding trunion, I'd much rather have the fixed stock trunion, the folding trunion on my Arsenal SLR104 is buttery smooth.

I'm well aware that some AKs will need some fitting here or there but the original part didn't even want to go back on.

This is the version that I have,
Attached File


This is the JMAC adaptor,
Attached File

Those pic rail inserts might not really be meant to fold, that's why their brace has its own folding hinge.  It's just there to be easily removed should you change out someday to a stock or something that is meant to fold on the pin.

That said, I also installed that JMac AR tube adaptor on my PSA 104 after I had SBR'd it, and found the same, it was way oversized to fit the trunnion.  I ended up filing and sanding a little at a time from the JMac adaptor until it fit.  Just the area around the pivot pin hole, on both the top and bottom surfaces.  I also had to ream out the pin hole a little bit as well to fit the original PSA pin.  Jmac probably oversizes the part a bit so people can fit them to their gun in case different manufacturers have different dimensions to their folding trunnions.

Once it was all done, I had a good tight fit, so just go slow and don't over do it.  Modifying the adaptor is easier and cheaper than doing the trunnion in case you mess up.

Yeah, I kinda figured filing on the adaptor was the way to go, I wouldn't be so irritated if the original part easily fit back on.

I really liked the JMac adaptor, but eventually switched from it because it annoyed me how it doesn't actually fold the stock flat.  I now use the SAG AR stock adaptor and it went on with much less fitting needed.

Jeez. No filing! Get the proper Allen wrench and loosen or tighten those two screws.