. . . . and what to look for
Notice the difference in how flat these primers are.
Examining the flatness of your fired primers is the best way to read
chamber pressure. It's important to keep an eye on this when you're reloading. These 4 fired cases clearly show the different degrees
of chamber pressure, and this is an accurate representation when reloading any caliber. If you pay close attention to your fired cases, and
you slowly work your way to hotter loads, you'll avoid seeing any of the "serious" pressure signs.
This explains what each primer is showing
- Very mild load (this is too mild).
- Mild load.
- This is an ideal load (could go just a bit hotter).
- Absolute Maximum load (approach this pressure very carefully).
Some brands of primers have a noticeably harder cup than others. This difference in primer hardness can cause very a slight
variation in your pressure readings. Seating bullets too short or too long will affect chamber pressure considerably, and some types of powder
will increase pressure as the outside temperature increases. When you develop maximum loads in the winter, beware of the pressure increase
when using those handloads in the heat of summer.
CAUTION: Most magnum calibers develop high pressure long before you start seeing flattened primers. Handloaders
should stick to the loads shown in published reloading manuals, and watch for "other" pressure signs. Other pressure signs include hard case extraction and
raised surface on the case head that align with the ejector hole in the bolt.