I'm going to swap out my Sig 556 retractable side folder for a original Swiss style side folder - Just checking to be careful with expensive parts -

Is it just punch out pin on hinge from top (downward) and replace and re-insert pin?

Thanks

PS I know the original style is a bit shorter, but going for early-classic Swiss look.  I can't help it I love those classic looks!

Where did you get the stock from?

Numrich / Gun Parts Company.  I could only order one (last one?) and it was $84!)  was listed under sig 556 parts.

I was ordering some parts for a Winchester 1907 project I got cheap and was looking for things to add to my cart to get the free shipping threshold and took a look at the Sig parts knowing CDNN had picked up some inventory thought Numrich may have too.  and lucky they had this.  CDNN has the AR stock adapters and the rail stock adapters for $30.

ETA

Numrich part
Stock, Folding, Used
PRODUCT #: 1643030
1 X $83.95 = $83.95

There’s a roll pin in the middle of the hinge pin I think. At least there was one in my 551a1 I previously owned; and, there’s one in my 553.

You are correct.  That is exactly how I changed mine. Knock the hinge pin out and replace.  There is a friction washer thats tricky to reinstall.  Just a bit tight.