Basically there are 3 headspace guages. The GO, NO GO, and FIELD. Go is the minimum headspace dimensions for the indicated caliber. The no go is the maximum headspace dimension for the caliber. The field guage is a enough larger than the no go guage(maximum headspace guage) that you can expect case failures. Excess headspace can caude erratic ignition which can indeed lead to fliers. What has happened is unknown but the rifle should indeed be inspected by a competant gunsmith. If the rifle is still shooting reasonably well it might be as simple a fix as setting the barrel back 1 thread and setting the headspace with a chamber reamer. For peace of mind I would have the bolt inspected for cracked lugs, although I would bet big money no cracks will be found. It mays simply be wear.. Look far galling on the lug faces.. Locking lugs on high powered rifles should be lubricated with a grease that will stay put..
