Article says they are being charged with having an explosive device.
At best, they were trespassing on range property and stealing brass. . .to me it appears they had unknowingly collected an unfired round. I say unknowingly because no one would put a live round in the middle of a bunch of brass and then try to melt it.
Could be unknowingly, or maybe they were ignorant of safety problems.
It did not just explode in a melter.
He was melting them himself to hide their provenance.
It also says: In the driveway, they allegedly found containers filled with disassembled 40 mm military munitions and three 81 mm mortar rounds that were still functional.
That's explosive devices.