The function of seating the primer into a case when reloading seems to be a very basic reloading step not worthy of consideration.  That said there are several errors reported by reloaders that have occurred.  The first is a primer complete flip around in seating and somehow inserted backwards with the priming compound visible.  In this configuration the primer would most likely detonate but the powder wouldn’t.  This condition would possibly damage the firing pin and possibly introduce gas cutting to the firing pin hole.  The next, a primer flipping 90 degrees sideways, this usually jams up the works, this primer must be removed or the case scrapped.  Best to switch to a de-priming die to remove it.  Obviously brass having the primer seated with either of these errors must be corrected.  We have been advised by those much wiser in ballistics to not de-prime live primers.  However, in either of these instances the primer has to be remove, or the case safely disposed of.  If you attempt removing a primer, go slow and careful, wear safety glasses.  If your press has a primer feeding system, remove all live primers to prevent a chain reaction detonation.  This has been known to happen and it can be a startling, deafening, and very dangerous, for certain remove all primers from the loading bench for maximum safety.  Ear protection is advised and if all is done carefully no problem will be encountered.   

Now on to the finer points.  As stated in another blog, primer anvils are not inserted into the cup all of the way by the manufacturer, this is intentional and not an error.  In seating a primer to the very bottom of the primer pocket it pushing the anvil into the primer cup the last few thousandths of an inch.  This slightly compresses the priming material makes the primer more sensitive or, activates it.  So, in seating the primer be certain you feel it bottom out in the pocket. 

One of the many functions provided by the Ultimate Cartridge Check System found at is to precisely check primer seating depth.  When seating a primer into a case it should be seated at least flush but preferably below flush, never protruding. This is critical for semi-auto firearms and important for consistent ignition in all firearms.  When using ammo in a semi-automatic firearm no one wants to close the bolt and be greeted with a slam fire, BOOM!  Many precision reloaders uniform the primer pocket making all the exact same depth and removing the minuscule radius in the bottom corner.  Numerous tools are available for this procedure.  If all cases have the pockets uniformed then primer seating is a breeze.  This is just one of the steps in precision reloading.  See Ultimate Cartridge Check System demonstration at or call (479) 629-5566  9am to 9pm central time Mon.-Sat. for information.

Tom Wilson                                                                                             5-14-2024 Fort Smith, AR ©

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