I'm considering alternatives to current gunpower or smokeless powders for bullet propellant. I ran across Sodium Azide, used for airbags mainly. If it is ignited, it starts a decomposition reactions which produces large quantities of N2 gas, fairly rapidly. Would this be any use for bullet propellant, in any capacity(even for niche uses)? Would it be a drop in replacement for smokeless powder, or would additional chemicals need to be added to catalyze the reaction?
Sodium azide has some shortcomings
an electronic controller detonates this mixture during an automobile crash:
$2 NaN_3 → 2 Na + 3 N_2$.
The same reaction occurs upon heating the salt to approximately 300 °C. The sodium that is formed is a potential hazard alone and, in automobile airbags, it is converted by reaction with other ingredients, such as potassium nitrate and silica. In the latter case, innocuous sodium silicates are generated.
About its safety
Sodium azide has caused deaths for decades. It is a severe poison. It possesses the NFPA 704's highest rating of 4 on the health scale. It may be fatal in contact with skin or if swallowed. Even minute amounts can cause symptoms. The toxicity of this compound is comparable to that of soluble alkali cyanides. No toxicity has been reported from spent airbags.
Sodium azide solutions react with metallic ions to precipitate metal azides, which can be shock sensitive and explosive. This should be considered for choosing a non-metallic transport container for sodium azide solutions in the laboratory.
It would create a lot of hassle to handle and fire the ammos, and if you go for the sodium silicate path, it will give a nice white puff when firing.