shoulder set-back

[Mr Peabody]

Thank You Larry Gibson!

[Eldon]

Solving the problem with CB loads is easy. Seat the boolit so that it contacts the lands. Then the case cannot move forward and will fireform to fit the chamber.

If you see primers backing out on RIMMED cases, you have excess headspace. Pretty common in old, hard used 94s.

Ditto belted cartridges which are all factory loaded with grossly undersized bodies and shoulders. Cases stretch all to heck, life is short but primers don't back out unless headspace is excessive.

[M-Tecs]

All primers back out and are reseated by case pressure. Even with zero headspace the primer that was below flush become flush after firing.

[popper]

So it appears the primary problem is with LP that have a small flash hole and large area under the primer. The tolerance of any chamber/ammo will allow the primer to move relative to the case. The primer MAY get smashed back into the pocket. Repeated light firings in the same case will show the accumulated set back. OK. Even fast pistol powder can't generate enough pressure (for light loads) to hold the case in place. Hypothesis validated by data. I still wonder about the case being pushed back from the boolit engraving? In my case, all brass is in the same bucket and may get a high pressure load next time, so I don't worry about it.

[Kestrel4k]

Earlier this year I was doing some light load work with a small batch of .308Win in my Win M88. After a few loading cycles, I started to get high primers but didn't really worry about it to begin with. That is, until I actually started to get failure-to-extracts; the fired primers were visibly higher than they used to be and the case rim appeared to be actually slipping past the extractor, setting the case further into the chamber. I set up false shoulders (w/ an 8mm expander) to get the cases under control, then did the #29 drill bit routine. Problem solved & primers are staying flush now - thanks LG.