The most familiar SXS actions, the Holland type sidelock and A-D boxlock do not utilise the main spring for anything other than primer striking. Other actions, notably the Beesley, Baker (12/20), utilise the main spring for opening after the primers have been struck.
Evn out of the action the pump and auto main springs are fairly mild compared to the stifness of double gun springs, and that goes for both coil and V types.
Somewhere there is a video of a SXS hammer gun tuned for cowboy action shooting. Its hammers can be easily cocked with the sweep of one hand. It is is probable that it strikes primers OK.
