I had a .22LR round detonate in the pocket of my hunting jacket with a 9v battery - down everywhere and two surpised teenagers who thought they were taking fire!! We did an interesting experiment later which involved a large sheet of plexiglass a cinder block and several rounds of ammo to include .22LR, .32ACP, .38 S&W and a lone .30-30 cartridge. No iPhone timers in those days so a sweep second hand had to do. It would probably get us sent to jail now, but we did learn that a 9v would set of a .32ACP much faster than it would a .30WCF.
Good times...