Dave,
You mentioned empty case extraction issues. My first question is does that mean he's trying to cycle empty cases from the magazine then extract and eject them? Or, does it mean after he has fired the rifle, he's trying to extract them? There is a different cause for each.
For cases from the magazine, the most common issue is the extractor isn't going over the rim. The most common cause is that he's sizing the cases (assuming he's reloading) with the shoulder set back too far. Or the chamber has the shoulder cut too deep.
For cases that fail to extract after fired, the most common cause is dirt or debris under the extractor. Although I've seen it caused by a bad plunger spring under the ejector. For a bad spring the case is pulled from the chamber but will drop about the time it's fully out of the chamber.
Hope this helps,
Ted
