I think seagiant nailed it. A quality barrel should have no issues with factory ammo, even straight out of the box. I'd be inclined to carefully inspect the barrel; gas port diameter, smoothness/cleanliness of the chamber, etc. It sounds like the bolt is doing its job; the chamber just isn't releasing the fired case.
For 5.56mm
Colt's gas port sizes are:
* 10.5" - .093
* 11.5" - .081
* 14.5" - .063
* 16" - .063