Are you saying that static electricity from the vacuum could set it off?
Walt
no..
If you look at the pressure gradient in a gun barrel, there are two areas where the pressure drops, or at least slows..
The first is where the bullet starts to move, overcoming the shot start resistance due to friction and/or bullet engraving and accelerates down the barrel. Until the bullet "unsticks" there is a pressure build-up. As the bullet moves down the barrel, the volume of the chamber increases and the pressure drops, relatively speaking. This causes a drop in temperature for an instant due to the working of the universal gas law PV/T being a constant. In practice this pulse only happens for a very short time, but is the reason for a ring of fouling to form just forward of the chamber caused by the condensation of some of the combustion products on the side of the barrel.
The same happens at the muzzle when the bullet exits and the pressure in the barrel drops to atmosphere. Again there is an instance of cooling caused by the drop in pressure, resulting in the condensation of residue just before the muzzle, hence the second ring of crud buildup!
This low pressure pulse can also cause slow burning propellent grains to drop below ignition temperature and be extinguished as they leave the muzzle. This typically occurs with slow burning nitro powders that have not reached all burned before getting half way down the barrel. In practice many nitro loads eject unburned powder which cannot sustain ignition at normal temperatures and pressures.
This is very rare with Black Powder propellent. Regardless of grain size Black Powder burns very quickly and is rarely ejected unburned from the barrel. Much of the residue from BP is either carbon or sulphur, and it is usually particles of these substances that create the sparks and burning embers from the barrel.
So.. nothing to do with static! It is entirely possible that the fire was started by a burning ember from a BP gun, however the hazard fire was as a result of unburned NITRO powder grains trapped in the Astroturf, not Black Powder grains!