I have a Daniel Defense M4 URG V2 upper that I sent back for some warranty work. I continued to have failure to feed issues with a variety of ammunition and was seeing that the rounds were getting caught up on the feed ramp. The barrel extension is textured and gritty almost like sandpaper. From all of my hundreds of hours cleaning M16s and M4 in the Marines and the national guard, I never remember barrel extensions being this way, they were always smooth steel. I returned the upper two weeks ago and today I get this reply. "The armor states he’s done quite a bit of work to it. He believes it may be the “Gritty” phosphate inside the barrel extension. So at this point we are going to replace the barrel. We don’t have them in stock now. As soon as they come into stock we will grab one and test it. I will see if we can get a time line." What do you all think of this reply? what do you think the issue is and does it warrant a new barrel? thanks for the input.