Excessive headspace will do a few things, but it will not cause a KB.A case fired in a much larger chamber will not create a high pressure spike. It's done all the time when fire forming cases. If the .243 case shoulder were set back excessively in the sizing operation creating excessive head space, it would likely case case head failure as in the picture. A minor case of excessive head space will frequently blow the primer from the pocket, especially with AR platforms. Sometimes the primer gets in the wrong place and ties up the action. Again, this is just conjecture, based on the picture.
str1
Excessive headspace will do a few things, but it will not cause a KB.
If the round is under powered or "weak" the primer will back out and stay backed out.
If the round is of higher pressure the primer will back out and then the primer will be forced back into the case causing a flattened primer giving the false impression of Excessive pressure.
No way a few (K) of excess headspace is going to turn a Safe load into a KB load, not going to happen.
Excessive headspace will do a few things, but it will not cause a KB.
If the round is under powered or "weak" the primer will back out and stay backed out.
If the round is of higher pressure the primer will back out and then the primer will be forced back into the case causing a flattened primer giving the false impression of Excessive pressure.
Having seen a couple of case failures as a result of excessive head space in rifles, we are just going to have to disagree.
str1
The Smith may have found excess headspace, but that was not the cause of the KB.
More likely the "competition" rifle had less freebore and the bullet was jammed into the lands.