Originally Posted by Mule Deer
Originally Posted by rcamuglia
Those primers don’t show over-pressure loads AFAIC.

Cratered due to an oversized firing pin hole, yes

Exactly--and the velocities agree with those listed for the ammo, and velocity is a far more reliable indication of pressure.

Primer appearance is the most over-rated "pressure indicator" for handloaders--and has been for decades. Which is why General Julian S. Hatcher, who spent most of his U.S. Army career in various aspects of internal and external ballistics, wrote in his still very relevant 1947 book Hatcher's Notebook, mentioned "the notoriously unreliable method of judging pressures by the appearance of the primer."

Unfortunately, Hatcher apparently believed the reasons for this were so obvious that he didn't describe the details. Which is why I did in chapter 30, "The least Reliable Pressure Indicator," of my 2020 Big Book of Gun Gack III.

Yet many handloaders still believe in primer appearance--and even a few handloading manuals still include it.


Yeah, flattened primers (which aren’t even shown here) aren’t a reliable sign of over-pressure. Short brass can cause flattened primers even with light loads.

The firing pin strikes the primer and forces the case forward a bit, ignites the powder which blows the primer out of the pocket some, then the powder ignites forcing the case back into the bolt face which reseats and flattenes the primer to fill the pocket.

His measured velocities aren’t unusual. Firing pin hole needs to be bushed.

Just a bad case, which I’ve never seen before

Originally Posted by Bristoe
The people wringing their hands over Trump's rhetoric don't know what time it is in America.