Anyone using a live 40mm round as a paperweight, let alone casually knocking it around, has no business "teaching" anything, to anybody, because they're an absolute idiot.
"..Colla had found the 40 mm round while hunting years ago, Huston said. He used it as a paperweight and "obviously he didn't think the round was live," Huston said.
"He'd had it for years and years and nothing had happened before," Huston said. He described the round as about an inch-and-a-half wide and about five inches long. .."
http://www.venturacountystar.com/vcs/ve/article/0,1375,VCS_251_4594189,00.html