I haven’t seen an independent study on primer harness, but I do know that manufacturers study this. SAAMI gives guidelines on how to test Primers. This involves seating a primer in a case and dropping a steel ball on a firing pin. The height of the steel ball determines the amount of force delivered to the firing pin.

The tests are caliber specific. A large sample (usually 100 tests) are done to statistically analyzed the primer. This test helps to weed out Primers that are both overly sensitive or Primers that are not sensitive enough.

Manufactures of Primers make many different types of Primers within a given size and type. Altering primer cup thickness, the mix and charge amount, as well as anvil design in order to comply with SAAMI standards. (If they are SAAMI member company or follow SAAMI guidelines). Only a very small amount are available to the Reloading market.

A particular case study, that I was involved with, was done on 300BLK which has a high misfire rate due to the very small shoulder. A term called “crush up” is used to describe the tendency for the firing pin’s force to be absorbed by the flexing of the small and thin shoulder. All cartridges that head space on the shoulder have a similar phenomenon but the 300Blk is especially bad due to the design of the case.

Adjustment to the case design as well as the primer had to be made in order to reduce the misfire rate. Obviously as a handloader these Primers and cases aren’t available to us. However it does show that if we are having issues with slam fires, pierced Primers, and duds. That we may need to look at the primer rather then blaming ourselves or the firearm.



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