After shooting maybe about 200 to 300 rounds I noticed a little play in the buttstock of my AR(it's an adjustable buttstock from DPMS I think). Upon removing it I found that the buffer tube was loose. I tightened the buffer tube up and put the buttstock on tight. Took it out again and after a couple hundred rounds I noticed again that there is a little play in the buttstock. Is it time for a new buffer tube or is this something that is characteristic for AR's? Any info on a fix would be appreciated.
                 Thanks

Normally, I will use BLUE loctite on the receiver extension threads, and on the lock ring threads to keep then in place. This allows me to install the ring without having to muscle up on getting the lock ring tight.

If I need to remove the extension at a later date, I just heat the receiver extension (not the receiver) to break the "BLUE" loctite bond.

Thanks for the information. I may try that. So through the act of shooting it's common that the buffer tube might come loose? I know there is quite a bit happening there with the bolt carrier being blown back into the tube and all but I just didn't know if it was common.  

Just to be a bit more precise, we are talking about the receiver extension (what you call a buffer tube) coming loose from the lower receiver, and not the telescoping butt stock being loose on the receiver extension (buffer tube).

If you mean that the telescoping butt stock is loose (some wiggle room) on the receiver extension, than that is normal, and will get worse over time.

As for the receiver extension coming loose, if the lock ring is tightened correctly, it should stay in place (even without loctite).  Just what tool are you using to tighten the lock ring?

I'm sorry but my description of my stock was not correct. What I meant is that I have a full stock with an adjustable butt-pad. And that it is working loose due to the receiver extension coming loose from the lower receiver. I took the thing apart this morning and have not seen a locking ring. There is only a screw that holds the buttstock to the receiver extension. I do think I am getting that tight enough when I tighten it down. Sorry for not being clear on my description.

You can still use the blue loctite to help keep the receiver extension tight.