Ruger Mk II failure mode

A fellow at the range today was having extraction and chambering issues.  It appears the extractor cut was filled with debris and the extractor had hammered it until the edge of the chamber was bent inwards.  Have you seen this failure mode before?

Never. Wow that's a lot of crud to lock up an extractor so it can't move and would batter the extractor notch in the barrel.
Jon

By any chance was it a range gun?

I believe the old Marvel .22 conversions had a similar issue.  In this case, the extractor would act as a claw and slowly scrape away metal until it started cutting into the chamber. 

I also have never heard of this happening on a Ruger or clone thereof...