I was told the rifle rounds where more dangerous, but not why. My suspicion is the plastic tube around a shotgun shell loses strength before the round is hot enough to go off ~200C. Though it’s probably more complicated.
As to humidity, I don’t know it might be just extreme humidity or it could be humidity + temperature, or perhaps we had a bad case of ammo to start with.
As to humidity, I don’t know it might be just extreme humidity or it could be humidity + temperature, or perhaps we had a bad case of ammo to start with.