I have a savage mk2 with the unthreaded varmint barrel on it that I've shot about 200 rds though with out a problem but the last 5 rounds I shot through it today all of a sudden the bolt is binding really bad and feels like sand is in the action. Gave it a good cleaning and light oiling and it's still doing the same thing. Anybody have any idea what could be causing it? I had some slight burrs that I did stone and then made to to throughly clean all the parts so there was no foreign material in it.