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Like powders, primers have a character that is all their own. Some burn longer and others burn with greater intensity. Some have a longer spark and produce heat over a much longer time – as long as several milliseconds lasts, that is – and this is referred to as the flame’s duration. In general, target loads do not need much spark, because the propellants are in the fast-burning, easily ignited category. Hunting loads, however, may require a great deal of primer boost and heat to get slow-burning propellants cooking. On a cold day, the need for tight crimps and warm primers can be critical to avoid sputtering ignition. For these loads, magnum primers were developed, an appellation that seems contrary to their typical application. Magnum primers are especially hot. Generally, however, magnum shotshells derive their power not from hotter primers but heavier shot payloads.

So do not fool yourself into believing that all primers are the same. They are not. Different primers produce varied results and cause distinct reactions as other shotshell components (type of powder, weight of load, shape of the hull) change. Although you would not want to have one explode in your closed fist, as the explosion would cause you permanent damage, by itself, a primer is not a significant pressure generator. While one type of primer produces minimal pressure in one load, another type might not. The same is true for maximum pressure. Except for this one thing – all arbitrary component-swapping creates new and unpredictable results – you cannot generalize about or substitute with primers. These small explosive elements and the energy they produce are a part of every load’s individual ballistic equation. Even if the pressure does not increase or decrease a great deal when you substitute the primer you have on hand rather than finding the primer you need, the balance created by a specific combination of components will suddenly be thrown off balance and the resulting load will be a below-average performer.