Inspired by Can you crit with the minus 5 from sharpshooter?.
It was asked if you could still crit with Sharpshooter's -5 to hit / +10 to damage option active, but that got me wondering — do you multiply that bonus damage, should you crit on your attack? At an additional 10-20 points, that could be a massive increase in damage.
Best Answer
No. Only damage dice are doubled - static modifiers like the +10 from Sharpshooter are unaffected by a critical hit.
(PHB p.196, emphasis mine)