When I was a kid I was given several hundred cartridges for use with pellet guns. I used a bunch for that purpose, but eventually got bored and started experimenting. The short version is that I found a number of ways to get the ends to rupture (moderately exciting, kind of loud) but never could get them to "explode", even by tossing them into the fire, duct taping them to railroad tracks, or shooting them with the pellet gun. So even if you encounter extreme conditions, you might get them to vent as described by Burton above, but I'd be pretty surprised if you could get one to rupture out the side, mimicking an explosion.