Powder or primer degradation


Well-Known Member
May 16, 2019
Orlando, Florida
There is a handful of things that blank primers.

Too much pressure - you have
Small cases with big firing pins - you have
Excessive headspace - dont know
Firing pins with improper shape - dont know
Too big of firing pin hole, loose - probably not
Thin cups on primers - dont know
Weak firing pin springs - dont know

I highly doubt firing pin length is your problem. The primer cup and anvil stop the firing pin not the stop collar. This is why the dent in you primer is usually shallower than firing pin protrusion.

You have two cases, with different head stamps, with severely flattened primers that are also punctured.

The cases with different headstamps that dont have severely flattened primers are nut punctured.

I can also tell by looking that you have a large dia firing pin. Much larger than is needed on such a small case. Common on older rifles. Also looks like it has a bit of an edge near the OD but cant see well enough.

Both high pressure and excessive headspace can make primers look flattened. Both can result in punctured primers.

Small cases build pressure faster than large cases. Primers push out of the pocket towards the boltface and over the firing pin much quicker.

Small cases are WAY more susceptible to pressure spikes due to volume or powder changes than large cases. 1gn variations to a 10gn charge is a 10% increase, to a 100gn charge its 1%.

Because only 2 cases have punctured primers, The same two with similar headstamps, the primers that are not punctured are neither flattened, cratered, or punctured.

Id say excessive pressure is most likely
Excessive headspace is 2nd
Wrong size or mis-shaped firing pin is 3rd

Check inside of bolt for primer bits
Check firing pin for flame cutting
Revert to starting charges and minimum headspace
Use fresh, thick cup primers
And im betting youll be just fine.

If you wanna be thorough, check the volume of the cases with punctured primers to one that isnt. If its smaller you know excessive pressure is the culprit.
The primers in question are not punctured just deep strike. I agree overpressure is the likely culprit. Perhaps the tow cases were slightly smaller volume. At any rate he is starting over and working up. BTW he is using 0.223, not 0.224 as his gun is 223. He said he ordered a box of 224 until he realized is was 223. Never used them but doesn't know where they are now so they possibly got mixed in.

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