carguychris - thanks for your very thorough response. As you were typing that, I was reading something very similar here:
http://surplusrifle.com/shooting2005...esbs/index.asp
Looks like I did not clean the rifle quite as thoroughly as I thought.
Extraction is good when the rifle is cold, so I think it is a lack of proper cleaning rather than a burr. Gives me something to do tonight after work.
Thanks again.