Ammunition doesn’t “expire” per se, but the gunpowder looses potency over time. The largest risk to shooting old ammunition isn’t a failure to fire, it’s the risk that you will actually fire the shot and it doesn’t have enough momentum to make it out the barrel. If this happens, the bullet becomes lodged in the barrel and becomes an obstruction for the next shot. This is a sure-fire way to destroy your firearm and possibly injure yourself in the process. If your shot ever sounds funny, safely unload the firearm and run a rod down the barrel to make sure the bullet isn’t stuck in there.