I've seen bullet jam fail to hold headspace against striker impact on the primer quite a number of times. Seems a pretty common thing, actually, in my experience.
I'm sure neck tension plays a role in that, obviously. But... My experience with a number of various chamberings over the years, is that heavy neck tension and firm contact with the lands is a recipe for vertical in the groups. I run about .0015 or less neck tension on everything, but usually have better luck with closer to .001 on lands jammed applications.
Have, once upon a time when dealing with a very famous bench rest 'smith who didn't know how to headspace an AI chamber, tried heavy neck tension during fireforming and still had failure to hold headspace on striker impact. Lubing cases was the easy answer for that rifle.
Long winded, didn't mean to be. But, just what I've seen, with a lot of rifles over a lot of years, jamming the bullet into the lands not holding headspace against firing pin strike has been fairly common.
- DAA
I'm sure neck tension plays a role in that, obviously. But... My experience with a number of various chamberings over the years, is that heavy neck tension and firm contact with the lands is a recipe for vertical in the groups. I run about .0015 or less neck tension on everything, but usually have better luck with closer to .001 on lands jammed applications.
Have, once upon a time when dealing with a very famous bench rest 'smith who didn't know how to headspace an AI chamber, tried heavy neck tension during fireforming and still had failure to hold headspace on striker impact. Lubing cases was the easy answer for that rifle.
Long winded, didn't mean to be. But, just what I've seen, with a lot of rifles over a lot of years, jamming the bullet into the lands not holding headspace against firing pin strike has been fairly common.
- DAA