the ice block and jug were to show how powerfull guns are and that they r not toys(duh). and the "knowing your calibers" connection to saftey is that even though a .220 swift and a .22 are the same size bullet, the .220 is not an exceptible choice for shooting squirrels and crows out of trees. i do relize that this was not brought up in the post, just throwing out an example.