Quick Question About Primers

[Mb1500]

I know they are supposed to be recessed say 0.003" to 0.005" when live, but are they supposed to be pushed flush after firing? Over pressure will cause them to protrude?

[Stumpkiller]

Flush is normal. Over-pressure will cause them to flatten out in the pocket, or flow around the firing pin, or even perforate. The edges should have the radius the unfired primers do.

Some will show a little flattening. Some are soft enough to be slightly flattened when being seated (so check before/after on loaded then fired ammo).

Soot around the primer is also a bad sign - over pressure or worn pockets.

Use a micrometer to measure the base diameter. Especially if you have hard extraction after firing. Also look for a mark where the brass has been driven into the ejector hole.

[OLEJOE]

Also check for ejector swipe where the bolt head rotated and the case didn't when opening the action after firing. Primers can protrude if the load is light when fireforming new brass.

[Robinhood]

Primer protruding after firing is an indication of excessive headspace.

[Zero333]

Flat primers are not necessarily an indication of OVER pressure.
Some primer cups are softer than others and will flatten at near max pressures and the harder cup primers will flatten when over max pressure.

[Mb1500]

This is shooting 30-06 factory 150grain loads. Every round out of 2 boxes pushed the primer flush.

[Robinhood]

50000 psi plus will push the primer against the bolt face making it even with the case base.


Edit: or even 42000 psi. Ed will be along soon to provide more detail.

[yobuck]

Cratering isn't necessarily a sign to be concerned about high pressure. A slightly oversized firing pin hole can contribute to that also.

[bigedp51]

Primer protruding after firing is an indication of excessive headspace.

My 30-30 Winchester 94 always has the primers protruding at 42,000 psi or 38,000 cup.

And all a protruding primer means is the chamber pressure was not great enough to cause the case to stretch and contact the bolt face.

A 30-30 at maximum SAAMI headspace of .070 and minimum SAAMI rim thickness you would have .017 head clearance.

Most 30-30 primers will back out .006 to .009 depending on rim thickness and if the rifle is between the GO and NO-GO gauges.

https://i.imgur.com/HK76WCp.jpg

NOTE, any time you make a workup load starting at the suggested starting load the primer will protrude from the rear of the case. Until the chamber pressure goes beyond the yield strength of the brass and the case stretches to meet the bolt face. And this depends on the inside diameter of the case and the hardness of the brass.