I've had my AR for about six months now and when I was cleaning it I noticed that the buffer retainer plunger has a groove worn in it. Is the buffer tube supposed to turn in and hold the plunger down or do you stop turning it in before it gets to the plunger?

Bob

Post a pic.

I'm not sure who did that, but it looks like your buffer was screwed in too far, and someone compensated for it by "v-notching" or cutting a "U groove" to clear the detent pin. It also appears the other side of the "v-notch" or "U groove" has sheared off, leaving you with one side left. It should probably still hold, but the tube should have only been threaded in enough to overlap (at all) the detent's shoulder (some barely kiss the pin, others don't. Not important. So long as the tube overlaps the shoulder). "V-notching" or "U grooving" could have weakened the original tube's lip (thus why one side is apparently missing).
My opinion?... tubes are cheap. Just put a new one on. Although that set up could still work fine, I'd not be happy with that. YMMV.

BTW: some people get obsessive about detent pin coverage. You'll see this when the  tube extends INTO (past) the upper ring. That should NEVER be (usually it's a tad behind the ring).

I figured it out. I put a little anti seize on the buffer tube threads when I put it together and there was some on top of the wide part of the plunger.

Bob

If the tube is centered as it should be that is a different style tube sold by Tapco on their mil spec tube. It is actually a better design and allows more coverage and flexiblity on timing the tube when installed. If you look at the additional image on the link you can see the offset lip in the pic.
http://www.tapco.com/products/ar/index.php?_a=viewProd&productId=133

I just uploaded mine at the same angle as your pic. Here is how they should usually look (notice the tube isn't threaded too far into the upper ring. There should be a small gap (recessed), not the tube protruding at the top, and the lower tube lip just covering the detent shoulder):



I'm not familiar with the OP's brand of tube, but that's not the mil spec way of doing it (not that it's wrong, I'm just not familiar with it).
It looks like someone filed away half of the lip on the OP's tube just to (unnecessarily) thread it in one more turn (which is now causing it to also protrude INTO the receiver).

Is this a pistol or a rifle buffer tube?

I'm the OP and didn't post the pict, that was someone else. My tube looks like the one Maverick posted, mine just had some anti-seize around that looked like it was worn.

Bob