My Colt Magnum Carry has a pretty thick manual.
This revolver may be carried in one of three modes to accomodate your needs:
Mode1
Cylinder empty, hammer down. revolver cannot be discharged. Use mode 1 for storage, cleaning, transportation, demonstration, dry practice or repair.
Open the cylinder when laying the revolver down, carrying it onto a range, or when handing it to someone else.
Mode 2:
Cylinder loaded with 5 rounds, empty chamber under hammer, hammer forward. Revolver cannot be discharged unless trigger is squeezed. Use mode 2 when carrying the revolver ready for use.
Mode 3
Cylinder loaded with 6 rounds, hammer forward. Revolver can be fired when trigger is squeezed. Use mode 3 only when you must have MAXIMUM FIREPOWEE IMMEDIATELY AVAILABLE.
(their emphasis)
At least Colt says you can PUT 6 in the damn thing.
Also:
"When YOU squeeze the trigger, YOU must expect the gun to fire. YOU must take full responsibilty for firing it. YOUR care can avoid accidental discharge and YOU will thereby avoid accidental injury and death."
That's a pretty good way to sum up WHY we have 4 rules.