That's a fact that a bullet travel farther than a pellet
Of course, there is no reason to use a sawed off shotgun at long range, that what make no sense
However, with the spread of the sawed off shotgun, there is already few little chance to deal damage farther than this range. It only prevent from lucky shotgun headshot at long range.
What you said sounds like shotgun are useless 0_o
Man, at close range you can kill in one shot anybody! Even boiler-plated guys.
If your ennemy is too far away, swap to your pistol.
For the winchester shotgun, we should take in consideration that this is much more valuable to aim for the head, while it's more valuable to aim for the torso with other shotgun. So we should not increase its damage too much. And this weapon is a good "fixer" (it prevent your target from moving away). Another advantage: it is very fast to reload it. In deathmatch, this is my favorite weapon when there are many people.
Of course, it needs testing to find the correct value.