Prior literature reporting increased rates of firearm-related homicide and suicide with increasing firearm availability is limited by only examining the availability of firearms, which is only one component of firearm-related mortality. The objective of the current study is to separate the rates into their respective components and determine which components contribute to mortality rate changes. To address the objective, nationally representative data from 2001 to 2012 was collected from a variety of publicly-available sources. Utilizing decompositional methodology, a negative binomial regression was used to estimate rate ratios for the association between the components and year category, and relative contributions of each component were calculated. From 2001 to 2012, the homicide and unintentional mortality rate decreased while the suicide rate increased. The suicide rate was only the firearm prevalence rate. The unintentional mortality rate was a factor of firearm prevalence, injury incidence, and case fatality rate. The homicide rate was a factor of firearm prevalence, violent crime rate, injury incidence, and case fatality rate. The current results suggest that the contributors of changes in firearm-related mortality are multi-faceted. Future studies should perform a decompositional analysis utilizing more granular data to examine whether the currently reported results are true associations or a factor of ecologic fallacy.