I was using PMC ammo - maybe that was the problem
I took it to the smith today and he said the problem was that the trigger housing had come loose and that (its a safety feature) had caused the rifle not to fire. I hadn't noticed but when he showed me it was obvious that the trigger housing had backed out of the action (step one in dis-assembly, I believe). He charged me $5 to hit it with a rubber mallet and knock it back in. Problem solved.