There are other ways to nerf guns than reducing the accuracy. I would much rather see the rifle's rate of fire reduced over seeing an accuracy drop. Luck is never a valid substitute for skill. Dropping the accuracy creates a luck factor in rifle-fights.
As for the shotgun, here's how I would change it. Right now, at medium to long range it is very lucky to hit an oppenent, but shots that hit do a good amount of damage. Instead of that, all shots should hit, but they should do far less damage past a certain point. It isn't a buff because the average damage would be the same for both cases, but skillful aim is better rewarded. This removes the dice-roll factor and at the same times keeps the current weapon balance intact.