Just wondering if this is the lock ring you are talking about?I have not had the pleasure of a clear lower yet, but I'll assume it's the same as this one.
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The lock ring on the outer buffer tube, if this is the ring your referring to,it is part of the KJ outer buffer tube. It has no use but to make it look like the RS counter part.The outer buffer slides over the inner brass tube and is held together with the receiver extension cap(part #52).And there is a set screw About 1 inch from the back as you can see in the photo.It keeps the outer from turning on the inner.
If you unscrew the extension cap (#52) and remove the set screw the outer slides off easily .