Lots we don't know here. Could still just be light loads or a poorly tuned rifle.
If the weather cooperates tomorrow I am going to try something to see if I can find a solution to my issue, I have a Rock River Lar 15, it ejects cases from just about everything I shoot at least ten feet or more, it will put 10 empty cases into a 24 inch circle. I am going to take the upper from my Build and slap it on to the Rock river lower, if the cases eject farther then I would assume the problem is with my lower, possibly the buffer spring, if nothing changes then I would tend to think it's the upper, I took the BCG apart and removed and cleaned the extractor, the extractor spring looks fine.
