Quote Originally Posted by 1944Colt
Hawkmoon, the powder is fully consumed, as in burned beyond its initial recognizable state and transformed into the propelling gasses.
Unless you've found an abundance of unburned powder grains littering the ground and the chronograph, I'd not believe it was unburned powder triggering the sensor. About the only arms that spew unburned powder are, for example, a 45-70 rifle shooting slower rifle powders at very low pressure.
I claim no expertise in the area under discussion but have observed the following: In our indoor range w/ it's concrete floor cut into sctions the resulting gaps could be easiliy light any time w/ a droppped match or lighted cigarette. We shot .22 rf & centerfire was 99% .45 ACP. When sweeping the .22 cases they and the accompanying debris could also be easily lit.

Not long after this was discovered we filled the offending cracks.

Not having read that gunpowder is 100% consumed in firing we labored under the assumption unburned pdr was the culprit!?

Ron