I took my Colt AR15 out shooting today to sight in my new sites and Eotech.  Everything went find for the first 100 rounds and then all of a sudden I started having chronic failures to eject.  What was happening was the fired case was still in the chamber and the point of the live round was wedged under fired case.  I could not drop the magazine because the live round was stuck.  I worked through the issue but the same thing happened over and over again.  As I continued to shoot I started to have stove pipes were the fired case would get stuck between the ejection port and the bolt.  

Any idea what may be causing this and how I can remedy it?  I had the front site changed out to a YHM flipup.  Could this be the problem?  It's really ashame too because my AR has been very reliable other than an issue I had with led fouling of the gas hole in the barrel due to shooting .22LR's and no 5.56 mm rounds.  

Thanks for you help.

Mac

Check your extractor lip for damage.  What color is your extractor spring and insert and how old are they?

check the carrier key and make sure it is tight, either an extractor or gas issue

It is possible that your YHM sight is cutting off some of your gas flow, too.  Check to make sure it is tight and not shifting around.  Did you notice your groups moving around at all?

Brass shavings jamming the ejector.

Completely strip your bolt, clean and lube, re-assemble and test fire  for function.

I checked the FSB and found the YHM flipup had moved forward.  My YHM is a screw on version which I thought would be easier to install. The truth of the matter is I should have purchased a pin in version instead because the screw type system slips, takes a lot of fooling around with to get it straight and can be put out of true very easily.  Live and learn I guess.

I wonder if YHM will let me upgrade to the pin on version?

Mark

Mac,
I can spot drill the barrel to give the set screws something to seat in if you want to bring it down.
This will help prevent it from moving fore and aft or rotating.