Remember, you are cocking AND firing the gun with just the trigger motion (that's where the 'Double' part of double action comes in). You get the heavier resistance from compressing the main spring. An average trigger pull for a DA wheelgun is around 9 or 10 pounds. "Light" is 8 pounds. I've shot DA wheelguns with 12 pound pulls (it didn't stay 12 pounds for long once I started breaking it in) and you can shoot a trigger that heavy with fair accuracy (but only fair) if you really pay attention to doing it right. To get a 5 pound DA trigger pull, for example, you'd end up having to lighten the main spring and that could lead to light primer strikes and a failure to fire.