It is also my understanding that a conventional fire ext. will not put a gunpowder fire out.
"It will auto ignite at 394F. To extinguish a gunpowder fire use massive amounts of water, be sure that the powder fire does not also include an electrical fire, as electrocution is possible. Call 911, get everyone clear, stay back, let the professionals handle what is left."
"Smokeless powders, once ignited, will burn until they are completely consumed. They provide their own oxygen for combustion and cannot be extinguished by depriving them of atmospheric oxygen. Since it is intended to burn, a smokeless powder fire is difficult to fight."
"One thing worth noting is that I don't think there is anything that will easily extinguish burning smokeless gun powder. It carries its own oxidizer, so it is difficult to interrupt its burning."
"I would think, since we're talking about putting out a possible powder fire, the gas ones would be troublesome, since they can "scatter" the fire due to it's high charged deployment,"
Another thing to note is if you are in a small room ... you could suffocate from all the burning gases and CO2 produced.
I would suggest that you still include a fire ext. in case you have another more common fire ignite.... but as for the powder... massive water might be your best choice.