How about some pics of the inside of the upper and bcg! What do you mean by "moving the gas block"? Were everything handloads or combo of factory and handloads? An issue I had with an AR243win was the throat was short and factory ammo when in battery would leave land marks on the bullets. Does it have an adjustable gb? Try this, take a sized case (no powder, primer or bullet) and insert it into the chamber, close the bolt and then manually eject it. Case/brass might not be sized at the base small enough? If you had headspace issues you wouldn't have ejection issues (excluding extractor not grabbing the rim).
PICS please!
I think he has an adjustable gas block