I took my brand new DPMS carbine 16" bL out to zero it yesterday.  I was using PMP 55gr rounds which I guess DPMS does not like.  I would have to dump a bunch of oil in to the chamber to get the wpn to cycle through a mag.  It seems that the spent cartrige would hang in the chamber and the extract claw would slip off.  It got better as the day went on and I would only have to dump oil every other mag.  I shot appox 300 rd yesterday. Obviously this is unsat, options as I see them

1.  Try milspec Ammo
2.  polish chamber (need some guidence)
3.  Send it back to DPMS

other thoughts are appreciated

Bub

Fully clean the rifle, and then use CLP to lightly lube the rifle.

It sounds as if you forgot the pull the rifle down; give it a good cleaning/lube before you started firing the rifle.

Also, it's not uncommon for the rifle to be a little finicky the first time out.  The surfaces around the feed ramps are still have a few tooling burs, which scrap the brass on loading/unloading, then transfer the flakes under the extractor claw.  If the rifle starts having the same problem on the next outing, pull the bolt/extractor off and clean out the flakes that are holding it slightly off the bolts front edge of the extractor channel.

Sounds like that may be it.  I had cleaned the wpn to the extent I would after a range which of course is not all that good.  I did have to tap a couple of rounds out with a cleaning rod during the first time out.  Thanks.

I have a DPMS rifle and I have the same problem with South African surplus.  After I shoot a few rounds it would start to leave the spent case in the chamber.  I just changed ammo but I was told to change the extractor.  You might want to try changing that and see what happens.

I had this problem with my DPMS 16 incher, back in July. Give Dave a call there, and tell him what is going on with it.
I will not go into detail what was wrong with mine. But they did take care of the problem.

Just try to be careful when you go dumping oil in the chamber. One can ruin a barrel by doing this if that oil makes it past the throat. This especially holds true with high-velocity rounds like the .223/5.56. Oil will not travel down the bore as fast as the bullet, thus resulting in expansion rings.

Not trying to insult anyone's intelligence here, just passing some FYI. Good luck on getting your rifle squared-away! [;)]

I have heard of this a lot with DPMS including the one I built. Seems like a lot of the DPMS barrels have a tight chamber. Even after polishing mine it was still too tight. I had to send it back to DPMS, they reamed the chamber and opened my gas port up and now it shoots like a machine.

I gave Dave a call and basically he said that it was the ammo.  I haven't had a chance to get the ammo he recomended but have some on the way.  I will see in a couple of days.

This seems to be a common problem on some of the DPMS rifles.  You should not put oil into the chamber or bore at all.  Oil in the chamber can cause it to be too slick.  The casing can be thrust rearward against the bolt and damage it.  I've heard that oil in the bore can 'cause the expansion rings as stated above.  Also, ammunition is dirty and oil will just allow all that dirt and grime to stick in the chamber which is not good.  If you choose to polish your chamber you should be careful and do it a little at a time for the same reasons stated above.  I had the same problems, I solved my problems, read this thread:

[url]http://www.ar15.com/forums/topic.html?b=3&f=12&t=169340[/url]

A 14.5" DPMS barrel I just worked on had short HS and a tight neck. Have opened the HS up enough to take the GO, am awaiting time to test fire to see if it runs. Deepening the HS cleaned up the tight neck.

Was this one of the CMMG/DPMS uppers?  Was it not taking the "GO" gauge previously?

It was a new build from DPMS, I don't know from who the owner bought it. It would accept the GO with undue force. Once the bolt was closed it had to be pried open. This was with MULTIPLE stripped bolts as I had tried swapping bolts instead of reaming the chamber as a check of the bolt. HS is still short for my standards but makes military minimum standards.