[Slamfire]

I am very suspicious of that powder you are using.

Unburnt powder will look yellow, sometimes gray, if my memory is correct. I have no idea why you are not getting good combustion. This whole situation makes no sense if you are using the proper powder, primers, and cases.

I would load some 223 shells with a known powder, say IMR 4895, Varget, and see if your AR functions.

If you have a chronograph that will tell if something anomalous, velocity wise, is going on.

Do not “add” more powder in the concept that your charges are low.