I would not continue shooting it the way it is. It’s giving you a lot of signs of over pressure. I would think it’s a chambering issue and like another member said the reamer ran to deep. Measure your fired cases and compare case dimensions to unfired rounds. I am not familiar with Blaser rifles. But generally to check head spacing you would need to remove the firing pin from the bolt and remove the ejector pin. Then you can use scotch tape on the case head and get an idea of headspacing. For them to be snapping like that it almost seems like the chambering is out of round.
Good luck!
Good luck!