impulse does not increase. Moreover, in such highly compressed charges, primer plume may not penetrate as deeply as normal; therefore, less surface area exists where primer plume cooling can occur, hence plume pressure can remain higher longer. This situation does not occur in most "normal" rifle loads.Testing Primer Impulse: Primer-Only versus Primer-Plus-Inert.
Since time for testing and volume of simulant material were both limited, we only tested the CCI-350 primer in this particular study – a primer which, according to the above tables and other test results, generates propulsive force this is similar to that produced by most Large Rifle primers. Results of this test are startling for a number of reasons. Despite very high bullet pull used (tight carbide sizer followed by 0.425-inch expander, and Brinell 14 hardness bullets, seated 0.385-inch into case, test shots moved all bullets >0.65-inch, which means that practically the entire bullet shank had engraved into the rifling.