I would be looking for wear on the camming surfaces that cock the hammer on that action.
If the pressure from the hammer strike is not immediately begun to be relieved
upon initial lever movement, you'll have the problem you describe. Hard firing pin
or not. I've seen it on single shots before. Wear at several points soon adds up to
a lot of delay.
I think the 1881's have a firing pin retraction spring - is it still there?