Help with 2013 Sig M400 pistol

Doc in Pa said:

I am trying to take the original buffer stock off of the firearm and install an adjustable stock. I have already took off the short barrel and installed a Larue 16 inch bbl. The Sig buffer is called “Sig Sauer Pistol receiver extension/buffer tube. It doesn’t have a regular castle nut, it is a 1 1/4 inch ring for the castle ring. Question is ? Do I remove the buffer tube like a regular buffer tube with a castle ring or HELP. Thanks for looking.

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jtallen83 said:

I forgot about that little feature on mine. I'm not taking mine off but it looks like you could turn it off with a wrench on the flats at the end of the tube, failing that a strap wrench should get good bite on that knurling, I don't see any staking on mine, betting the rough edge of the knurling gives it a bit of a lock washer effect, knowing Sig it's gonna be insanely tight, welded with a locker, or both!

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