Lee press primer warning

[zchaparral]

I don't understand what would cause a primer to ignite in a press. I've had a couple of cases where a primer rotated 90 degrees, in both cases it repeated the second try in the same case and was then discarded. I don't have a lee press, but does anyone know how this can happen? If this has happened to you please tell your story.

 

[Rico567]

I don't understand what would cause a primer to ignite in a press. I've had a couple of cases where a primer rotated 90 degrees, in both cases it repeated the second try in the same case and was then discarded. I don't have a lee press, but does anyone know how this can happen? If this has happened to you please tell your story.

The Boxer primer we use to reload has three elements: a metal cup, a metal anvil, and the priming compound between them. The primer is ignited when crushed between the cup material and the anvil. This has to occur more or less "sharply," a gradual crush may not achieve ignition. There are certain conditions when a primer can be caught in a priming mechanism in a press whereby it is crushed and ignited. With the large numbers of primers in an automatic primer feed, this could result in a significant explosion if multiple primers detonate.
The discussion here has largely centered around the validity of some manufacturers' injunctions against using certain brands of primers, or "only use X and Y." The reason, presumably, is that some brands are more easily ignited than others. My personal view of all that is that these injunctions and disclaimers about primers are just legalese, put in the instructions at the behest of the manufacturers' lawyers.

Most people never have a primer go of in a press. I've been reloading shotguns, rifles, and pistols for nearly 50 years, and it's never happened to me. However, it CAN and it HAS happened.