The custom of loading 5 (actually, loading 1, skipping 1, loading 4) became standard procedure for percussion revolvers because they did not have a reliable safety mechanism. It really applies to guns that will be carried loaded and do not have a provision for resting the hammer in a safe place. Some percussion revolvers have between-chamber positions that lessen the risk of unplanned discharge but none are considered completely safe. Even with those designs there is a scenario in which the hammer slips while being moved from the between-chamber position to half-cock on a full chamber, or inadvertently when the gun is being holstered resulting in an unplanned discharge. The empty chamber rest position reduces the risk even further and is therefore preferred at organized events.
It is also good safety practice to make an empty carry chamber a routine practice on all your guns so that it becomes the natural thing to do even when carrying a gun with between-chamber rests. If you do that it will be less likely you will make a mistake and rely on that practice with a gun that either does not have the feature or has one that is not reliable.
Always follow the safest, most reliable practices.
