Brisance
The difference between standard and magnum primers is not measured by which one is hotter, but by which one has more “brisance” or shattering capability.
Definition:
Brisance is the shattering capability of a high explosive, determined mainly by its detonation pressure. The term originates from the French verb "briser", which means to break or shatter. Brisance is of practical importance for determining the effectiveness of an explosion in fragmenting shells, bomb casings, grenades, structures, and the like.
Fragmentation occurs by the action of the transmitted shock wave, the strength of which depends on the detonation pressure of the explosive. Generally, the higher this pressure, the finer the fragments generated. High detonation pressure correlates with high detonation velocity, the speed at which the detonation wave propagates through the explosive, but not necessarily with the explosive's total energy (or work capacity), some of which may be released after passage of the detonation wave. A more brisant explosive, therefore, projects smaller fragments but not necessarily at a higher velocity than a less brisant one.
The sand crush test is commonly used to determine the relative brisance in comparison to TNT (which is considered a standard reference for many purposes). No single test is capable of directly comparing the explosive properties of two or more compounds;[citation needed] it is important to examine the data from several such tests[citation needed] (sand crush, trauzl lead block test, and so forth) in order to gauge relative brisance. True values for comparison require field experiments.[citation needed]
I can’t comment as to the efficacy of the magnum primer over the standard primer. Perhaps someone with experience could chime in here.
