1. Regarding your issues with the KNS pin, you are not the only one, I have read that the best replacement take down pins are from CO gun sales, no complains of looseness, rather the fit is perfect and sometimes better than OEM. Perfect timing as there is a group buy going on right now to get them at a discount, so if you jump in then we are almost there to get the first tier of discount for the best replacement take down pins I know of. In my case I am getting either 4 or 6 pairs. 1 pair for my 1st gen ER/M4 style 556, where the front pins take two screw drivers (or dimes as the manual states) to unscrew the pin from both sides at the same time, totally sucks. My rear pin has become loose to where it easily falls out, and while I could fix it, I would rather replace it with one of these pins as I can completely remove it and that makes cleaning easier, and I want them to match cos of my OCD :). 2nd set is for my new 556R(ussian), which I bought brand new, so basically it doesn’t need them (yet), front pin is indeed tight as heck but I figure I can work it out over time, and rear capture pins is fine, but again, I like to get while the gettin is cheap. 3rd pair is for that 522 assuming I can confirm that the takedown pins are the same as for the 556’s. Given the 522 had some corners cut to hit its price point, I am assuming that the pins could use upgrading to improve the upper to lower “tightness”.

    Here is the group buy thread, it just kicked off like a week ago and they are still gathering buyers.



    1. Thanks, Mike. I checked the link in your second comment, but wasn’t sure if it will fit on the newer 556 variants. The page simply says: “These are meant to replace the double screw on all original style SIG Sauer 556.” The KNS pin actually seemed a bit too short, which is why I think the button didn’t extend up all the way when installed (while the button worked fine when not installed). I’ll jump in on that group buy if I can confirm that they’ll fit and operate properly in the later-model 556. Does anyone on that forum thread know if they will?


  2. I have read of several on the sig556forums that have used these pins to replace their TD pins in their second gen 556’s with good results. Regardless, to make sure that is supported (so that you can swap return the pins with no penalty if they don’t work), I just emailed them to ask, I will post their response here for posterity.

  3. Mike

    I want to add a threaded barrel to my MK 25 also, but have always been told it needs to be “professionally fitted” to the gun by a gunsmith? I want a genuine Sig Sauer barrel, and preferably the phosphate coated one, although I am having a tough time finding one.
    What did you do about the “fitting” aspect of the barrel install?


    1. If you get a genuine Sig barrel, it will just plop in without any special fitting requirements.


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