The chamber is clear - I can single load a round just fine. The problem is when I try to chamber a round from the magazine. The bolt goes forward a little, then stops. I found that if I pull the bolt back and then push really hard, then the round will feed and chamber. Afterwards, I opened the bolt and looked towards the side plate and I could see a thin line of what looks like brass. I have new Hornady cases - could the rim diameter be too large?

Yes, the machined off knob on the bolt makes it hard to disassemble it.