There's far more risk of old ammo NOT going boom than going boom in any harmful manner, and zero chance of it going boom just through casual handling. Here's the deal: a bullet needs a gun barrel to concentrate the pressure of the explosion in order to accelerate. No pressure, no acceleration. This is why ammunition isn't even considered a hazard by firefighters in a fire. Even if it gets hot enough to cook off, the bullet just pops out of the casing and falls. Just about nothing short of a .50 BMG poses any kind of risk whatsoever. Basically, it's not going to go boom, and even if it did, it wouldn't really hurt you.