I was cleaning my rifle today and I noticed that in front of the gas block on the barrel that there was a ring of exhaust leak all the way around the barrel about 1/8" wide in front of the gas block.  It stood out very clearly because I have a stainless barrel.  Is this normal or not??  The reason I'm asking is because the last time I was at the range every once in awhile the rifle would not chamber the next round after shooting.  I could pop off about 20 rds and then the next 4 wouldnt chamber correctly.  If  I pulled back on the charge handle it would load them manually.  It is a brand new DPMS upper.  Or am I just having problems until everything wears in since the upper is new??  I do have everything lubed up decently with CLP.  Today I gave it a really good cleaning with brake clean and relubed everything that moves.  Any information would be a great help.